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  • Chemistry  (49,600)
  • Inorganic Chemistry  (6,780)
  • Cell & Developmental Biology  (5,806)
  • Ecology
  • 2020-2023  (25)
  • 1985-1989  (46,601)
  • 1935-1939  (8,847)
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  • 1
    Publication Date: 2022-03-17
    Description: Coccolithophores were collected at 21 stations during summer 2016, from coastal and offshore areas of the Central Mediterranean Sea, to describe the ecology of the coccolithophore community integrating information on their abundance, environmental parameters (salinity, temperature, dissolved oxygen, and fluorescence) and oceanographic data. Emiliania huxleyi dominated the assemblage from surface to intermediate layers, while Florisphaera profunda was more abundant in the deep photic zone. Principal Component Analysis revealed that the distribution of coccolithophore taxa was influenced by environmental parameters: K-strategist taxa were related to warm surface waters, whereas lower photic zone taxa were influenced by the development of a Deep Chlorophyll Maximum and high salinity values, well below the thermocline. These results confirmed that a vertical species zonation, as a typical feature of low-middle latitude, characterizes the Central Mediterranean during summer. The distribution of F. profunda once again confirmed its use as a proxy of Deep Chlorophyll Maximum development and paleoproductivity estimates. Gephyrocapsa spp. (=total Gephyrocapsa), and in particular G. oceanica, were more abundant along the Atlantic Water pathway. Finally, the high concentration value of Helicosphaera carteri, recorded in the Ligurian Sea at an offshore station, suggested an expansion of the opportunist nature of this taxon from coastal environments to the offshore areas characterized by high turbidity and high productivity.
    Description: Published
    Description: 101995
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Keywords: Living coccolithophores ; Helicosphaera carteri ; Oceanography ; Ecology ; Central Mediterranean Sea ; coccolithophore ecology and oceanography
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: Coral reefs in the US Virgin Islands
    Description: These data describe the results of surveys of coral reefs at 10 m depth at 12 sites around St. Thomas and St. John, US Virgin Islands from 2011-2021 (up to 4 surveys). These results will be published in Edmunds & Smith (2022). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/872285
    Description: NSF Division of Ocean Sciences (NSF OCE) OCE-2019992
    Description: 2022-04-30
    Keywords: Coral reef ; Ecology ; Time series ; US Virgin Islands
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marlow, J., Anderson, R., Reysenbach, A.-L., Seewald, J., Shank, T., Teske, A., Wanless, V., & Soule, S. New opportunities and untapped scientific potential in the abyssal ocean. Frontiers in Marine Science, 8, (2022): 798943, https://doi.org/10.3389./fmars.2021.798943
    Description: The abyssal ocean covers more than half of the Earth’s surface, yet remains understudied and underappreciated. In this Perspectives article, we mark the occasion of the Deep Submergence Vehicle Alvin’s increased depth range (from 4500 to 6500 m) to highlight the scientific potential of the abyssal seafloor. From a geologic perspective, ultra-slow spreading mid-ocean ridges, Petit Spot volcanism, transform faults, and subduction zones put the full life cycle of oceanic crust on display in the abyss, revealing constructive and destructive forces over wide ranges in time and space. Geochemically, the abyssal pressure regime influences the solubility of constituents such as silica and carbonate, and extremely high-temperature fluid-rock reactions in the shallow subsurface lead to distinctive and potentially unique geochemical profiles. Microbial residents range from low-abundance, low-energy communities on the abyssal plains to fast growing thermophiles at hydrothermal vents. Given its spatial extent and position as an intermediate zone between coastal and deep hadal settings, the abyss represents a lynchpin in global-scale processes such as nutrient and energy flux, population structure, and biogeographic diversity. Taken together, the abyssal ocean contributes critical ecosystem services while facing acute and diffuse anthropogenic threats from deep-sea mining, pollution, and climate change.
    Description: We would like to thank the National Science Foundation for their support through grants NSF 2009117 and 2129431 to SAS.
    Keywords: Abyssal ocean ; Geochemistry ; Microbiology ; Geology ; Ecology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-05-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aguado, M. T., Ponz-Segrelles, G., Glasby, C. J., Ribeiro, R. P., Nakamura, M., Oguchi, K., Omori, A., Kohtsuka, H., Fisher, C., Ise, Y., Jimi, N., & Miura, T. Ramisyllis kingghidorahi n. Sp., a new branching annelid from Japan. Organisms Diversity & Evolution. (2022), https://doi.org/10.1007/s13127-021-00538-4.
    Description: Among over 20,000 species of Annelida, only two branching species with a highly modified body-pattern are known until now: the Syllidae Syllis ramosa McIntosh, 1879, and Ramisyllis multicaudata Glasby et al. (Zoological Journal of the Linnean Society, 164, 481–497, 2012). Both have unusual ramified bodies with one head and multiple branches and live inside the canals of host sponges. Using an integrative approach (combining morphology, internal anatomy, ecology, phylogeny, genetic divergence, and the complete mitochondrial genome), we describe a new branching species from Japan, Ramisyllis kingghidorahi n. sp., inhabiting an undescribed species of Petrosia (Porifera: Demospongiae) from shallow waters. We compare the new species with its closest relative, R. multicaudata; emend the diagnosis of Ramisyllis; and discuss previous reports of S. ramosa. This study suggests a much higher diversity of branching syllids than currently known. Finally, we discuss possible explanations for the feeding behaviour in the new species in relation to its highly ciliated wall of the digestive tubes (especially at the distal branches and anus), and provide a hypothesis for the evolution of branching body patterns as the result of an adaptation to the host sponge labyrinthic canal system.
    Description: Open Access funding enabled and organized by Projekt DEAL. This study was financed by the Biodiversitätsmuseum (PI:MTA), Georg August University, Göttingen, and by Grant-in Aid for Scientific Research A (No. 18H04006) (PI:TM) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. GP-S was supported by the “Contratos Predoctorales para la Formación de Doctores 2016” program of MINECO, Spain (code: BES-2016–076419), co-financed by the European Social Found. RPR was supported by the program “Contratos predoctorales para Formación de Personal Investigador, FPI-UAM,” Universidad Autónoma de Madrid.
    Keywords: Mitochondrial genome ; Phylogenetics ; Sponge ; Syllidae ; Symbiosis ; Morphology ; Anatomy ; Ecology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-03-09
    Description: Abstract
    Description: 1.Nature conservation is fostered through the expansion of protected areas. This is particularly evident in Sub-Saharan Africa (SSA), where conservation is intended to simultaneously promote the recovery of megafauna like elephants. Rising numbers of megaherbivores induce woody biomass losses but restore soil organic carbon (SOC). We hypothesized that increases of SOC under conservation with wildlife in SSA go directly along with increases in the preservation of plant residues in soil organic matter (SOM), traceable by plant biomarkers such as lignin and n-alkane. In contrast, intensification with agriculture leads to a reduction of them. To test this, we sampled topsoil (0-10 cm) and corresponding plant samples along different intensities of conservation and intensification in the Zambezi Region of Namibia, comprising a) conservation sites with low, medium and high elephant densities and b) adjacent intensification sites with rangeland and cropland. We found that lignin and n-alkane patterns of the above-ground vegetation were preserved in the soil. Confirming our hypothesis, increasing SOC contents with rising elephant densities went along with increasing accumulation of lignin-derived phenols. Under conservation, lignin concentrations were influenced by the input of woody debris into the soil, traced by carbon isotopes, clay, and total woody biomass. This could not be proved for n-alkanes. Under intensification, lignin derived phenols were lower than under conservation, but again, there was no clear pattern for n-alkanes. We showed that conservation with wildlife leads to an increase of SOC, which was accompanied by an accumulation of lignin-derived phenols in the soil organic matter. Increased input of woody debris, clay content and total biomass were important parameters for this lignin accumulation. In contrast, intensification with agriculture leads to a loss of lignin. Contrary, n- alkanes were not sensitive to detect effects of conservation or intensification. We conclude that increasing incorporation of woody residues into soil is a key mechanism controlling SOC accrual and to offset losses of aboveground biomass on SOC in sites under conservation with wildlife. The dataset contains raw data of lignin and n-alkanes and related soil properties. A third sheet contains a legend with information on abbreviations.
    Keywords: Ecology ; Environment ; Conservation ; Intensification ; Soil Organic Carbon ; Carbon Storage Dynamics ; Carbon Sequestration ; Biomarker ; Lignin ; n-Alkanes
    Type: Dataset , Microsoft excel file
    Format: MS Excel
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  • 6
    Publication Date: 2022-10-31
    Description: Dataset: Linear growth and competitive ability of PAC, Tables 1 and 2
    Description: Interactions of scleractinian corals with Peyssonnelid Algal Crusts were recorded at two sites and depth in Great Lameshur Bay, St. John, USVI. Since PAC in St. John is more abundant in shallow (3–5 m) versus deep (5–9 m) water, surveys were designed to contrast PAC between depths (3 and 9 meters). The first categorization of coral-PAC interactions at the Cabritte Horn and Tektite sites was August 2019, and the re-categorization was January 2020. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836304
    Description: NSF Division of Environmental Biology (NSF DEB) DEB-1350146, NSF Division of Ocean Sciences (NSF OCE) OCE-1756678
    Keywords: Macroalgae ; Scleractinia ; Ecology ; Competition
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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  • 7
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: Linear growth and competitive ability of PAC, Figure 3
    Description: Growth rate of Peyssonnelid Algal Crusts was measured using terracotta settlement tiles at five sites across Lameshur Bay, St. John, USVI. Unglazed terracotta tiles (15 × 15 × 1 cm) originally were deployed to measure coral recruitment, and photographs of the tiles were re-purposed to provide an additional measure of the planar growth of PAC. Years for which photographs of settlement tiles were available to be analyzed for growth rate include 2009, 2011-2012, and 2014-2019. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836164
    Description: NSF Division of Environmental Biology (NSF DEB) DEB-1350146, NSF Division of Ocean Sciences (NSF OCE) OCE-1756678
    Keywords: Macroalgae ; Scleractinia ; Ecology ; Competition
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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  • 8
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: Linear growth and competitive ability of PAC, Figure 2a
    Description: Percent cover of Peyssonnelid Algal Crusts was measured at two sites and depths in Great Lameshur Bay, St. John, USVI in July and August 2019. These sites (Cabritte Horn and Tektite) were selected because the abundance of PAC has been measured in these locations since 2015. Peyssonnelid Algal Crust was surveyed in quadrats placed at random positions along transects positioned haphazardly along the 3 meter and 9 meter isobaths. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836071
    Description: NSF Division of Environmental Biology (NSF DEB) DEB-1350146, NSF Division of Ocean Sciences (NSF OCE) OCE-1756678
    Keywords: Macroalgae ; Scleractinia ; Ecology ; Competition
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu
    Publication Date: 2022-10-31
    Description: Dataset: Linear growth and competitive ability of PAC, Figure 2b
    Description: The growth rate of Peyssonnelid Algal Crusts was measured at two sites (Cabritte Horn and Tektite) and two depths (3 and 9 meters) in Great Lameshur Bay, St. John, USVI. The growth rate of the PAC margin (micrometer/day) was calculated using the number of days between when the tag was initially deployed to mark the margin of PAC in August 2019 to when the margin was re-measured again in January 2020. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/836097
    Description: NSF Division of Environmental Biology (NSF DEB) DEB-1350146, NSF Division of Ocean Sciences (NSF OCE) OCE-1756381
    Keywords: Macroalgae ; Scleractinia ; Ecology ; Competition
    Repository Name: Woods Hole Open Access Server
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  • 10
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    Bay of Bengal Large Marine Ecosystem Project (BOBLME) | Phuket, Thailand
    In:  http://aquaticcommons.org/id/eprint/19148 | 17435 | 2016-01-08 11:53:29 | 19148 | Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Publication Date: 2022-08-02
    Description: The goals of the workshop were to: present verified data, draft a report containing visual descriptors and information on the structure and function of BOBLME ecosystems; identify information gaps and transboundary issues and develop capacity of national scientists on data integration techniques.
    Description: FAO
    Description: Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Description: The Bay of Bengal Large Marine Ecosystem Project (BOBLME) was supported by the Global Environment Facility, the Food and Agriculture Organisation of the United Nations, the governments of Norway and Sweden. The project was executed by the Food and Agriculture Organisation of the United Nations.
    Keywords: Ecology ; Information Management ; Bay of Bengal ; ecosystems ; data integration techniques ; transboundary issues
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 70
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  • 11
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    Bay of Bengal Large Marine Ecosystem Project (BOBLME) | Phuket, Thailand
    In:  http://aquaticcommons.org/id/eprint/19203 | 17435 | 2016-01-08 11:19:47 | 19203 | Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Publication Date: 2022-08-02
    Description: The workshop's aim was to consolidate and validate the information collected by the CSIRO project during the first regional ecosystem characterisation workshop held in February. This information includes; descriptions of broad scale biophysical drivers of ecological systems in the region; and descriptive narratives and illustrations of each ecosystem sub-region in the Bay of Bengal.
    Description: FAO
    Description: Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Description: The Bay of Bengal Large Marine Ecosystem Project (BOBLME) was supported by the Global Environment Facility, the Food and Agriculture Organisation of the United Nations, the governments of Norway and Sweden. The project was executed by the Food and Agriculture Organisation of the United Nations.
    Keywords: Ecology ; Information Management ; Bay of Bengal ; ecosystem characterisation ; biophysical drivers ; CSIRO
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 16
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  • 12
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    Bay of Bengal Large Marine Ecosystem Project (BOBLME) | Phuket, Thailand
    In:  http://aquaticcommons.org/id/eprint/19204 | 17435 | 2016-01-08 11:45:26 | 19204 | Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Publication Date: 2022-08-02
    Description: The workshop's objective was to provide information to improve a regional Ecopath with Ecoism (EwE) model.The workshop described the basis and principles underlying the software, encompassing the basics of Ecopath to Ecospace, economics and management strategy evaluation.
    Description: FAO
    Description: Bay of Bengal Large Marine Ecosystem Project (BOBLME)
    Description: The Bay of Bengal Large Marine Ecosystem Project (BOBLME) was supported by the Global Environment Facility, the Food and Agriculture Organisation of the United Nations, the governments of Norway and Sweden. The project was executed by the Food and Agriculture Organisation of the United Nations.
    Keywords: Ecology ; Information Management ; Bay of Bengal ; Ecopath with Ecoism (EwE) ; software ; economics
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 39
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  • 13
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26299 | 23782 | 2019-03-27 06:00:01 | 26299 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Keywords: Chemistry ; Fisheries ; Malaysia ; Pesticides ; Biological sampling ; Fish ; Fishery products ; Biochemical analysis ; Lethal limits
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 71-74
    Format: 4
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  • 14
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26300 | 23782 | 2019-03-27 05:58:36 | 26300 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Keywords: Aquaculture ; Chemistry ; Fisheries ; Myanmar ; Pesticides ; Biological sampling ; Fish ; Fishery products ; Lethal limits
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 75-83
    Format: 9
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  • 15
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26303 | 23782 | 2019-03-27 05:51:15 | 26303 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Keywords: Chemistry ; Fisheries ; Thailand ; Pesticides ; Biological sampling ; Fish ; Fishery products ; Dried products ; Lethal limits
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 100-105
    Format: 6
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  • 16
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26826 | 23782 | 2019-11-21 00:56:12 | 26826 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Presented in the paper is the standard procedure in the determination of K value which is an index to measure the enzymatic freshness of fish and squid. Specifically, reagents, apparatus and the analytical procedures needed and the calculations are presented.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Chemical analysis ; Fishery products ; Fish inspection ; Fishery industry ; Food technology ; Standards ; Specifications
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: B-6.1-B-6.7
    Format: 7
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  • 17
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26825 | 23782 | 2019-11-21 00:52:35 | 26825 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Presented in the paper is the standard procedure in measuring K value in fish meat by means of the freshness testing paper technique.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Chemical analysis ; Fishery products ; Fish inspection ; Fishery industry ; Food technology ; Standards ; Specifications
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: B-7.1-B-7.2
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  • 18
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26802 | 23782 | 2019-11-12 05:28:20 | 26802 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Presented in the paper is the standard procedure in the measurement of pH in the fresh fish meat. Specifically, the procedures in sampling and sample preparation, apparatus and reagents required, and the analytical procedures are presented.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Chemical analysis ; Microbiological analysis ; Fishery products ; Processed fishery products ; Fish inspection ; Fishery industry ; Food additives ; Food technology ; Standards ; Specifications ; pH
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
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    Format: A-3.1-A-3.2
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  • 19
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26842 | 23782 | 2019-11-15 07:54:48 | 26842 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Starch is commonly used in the production of fish jelly products as an extender and as binding agent. The paper provides the methodology in the determination of starch in fish jelly products. Instructions for sample preparation and the reagents needed are presented. Detailed procedures in the determination of the starch in a sample are provided.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Chemical analysis ; Fishery products ; Fishery industry ; Food technology ; Standards ; Specifications ; Starch ; Additives ; Food additives
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
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    Format: D-4.1-D-4.4
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  • 20
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26852 | 23782 | 2019-11-15 07:36:44 | 26852 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Cholera is an acute specific infection caused by the organism, Vibrio cholera. Diagnosis may be confirmed by the presence of large numbers of the comma-shaped bacilli on direct microscopic examination of a fecal or vomitus smear, and by the isolation of the organism on culture. Fish and shellfish have been identified as vehicles of cholera. Large numbers of V. cholera must usually be ingested to cause cholera. Thus problems often occur when poor handling and inadequate refrigeration have allowed the organism to multiply. Presented in the paper is the methodology of determining the presence of Vibrio cholera in fish and fishery products.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Fishery products ; Fishery industry ; Food technology ; Standards ; Specifications ; Aerobic bacteria ; Microbiological analysis ; Microorganisms ; Pathogenic bacteria ; Pathogens ; Health and safety ; Public health ; Microbial contamination ; Vibrio cholerae
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: E-7.1-E-7.5
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  • 21
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26843 | 23782 | 2019-11-15 07:52:55 | 26843 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Sodium chloride is an important additive for the production of fish jelly products. It extracts the salt soluble protein to give the gel strength of the final product. The paper provides the methodology in the determination of the amount of sodium chloride in fish jelly products. Instructions for sample preparation and the reagents needed are presented. Detailed procedures in the determination of the salt in a sample are provided.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Chemical analysis ; Fishery products ; Fishery industry ; Food technology ; Standards ; Specifications ; Additives ; Food additives ; Salts ; Sodium chloride
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: D-5.1-D-5.2
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  • 22
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    Marine Fisheries Research Department, Southeast Asian Fisheries Development Center | Singapore
    In:  http://aquaticcommons.org/id/eprint/26851 | 23782 | 2019-11-14 01:29:31 | 26851 | Southeast Asian Fisheries Development Center, Marine Fisheries Research Department
    Publication Date: 2022-08-02
    Description: Food poisoning due to Vibrio parahaemolyticus is a food-borne infection resulting from the ingestion of a large number of this organism (about 106-109 viable cells). The major symptoms are diarrhea and abdominal pain with headache, fever, and vomiting also occurring. The organisms are excreted during the acute stage of the illness after which they decrease rapidly. The differentiation of V. parahaemolyticus from other pathogenic species of Vibrio is based mainly on salt tolerance, Voges-Proskauer reaction, fermentation of sucrose, and growth at 43°C. Presented in the paper is the methodology of determining the presence of Vibrio cholera in fish and fishery products.
    Keywords: Chemistry ; Fisheries ; Manuals ; Culture media ; Analysis ; Analytical techniques ; Methodology ; Fishery products ; Fishery industry ; Food technology ; Standards ; Specifications ; Aerobic bacteria ; Microbiological analysis ; Microorganisms ; Pathogenic bacteria ; Pathogens ; Health and safety ; Public health ; Microbial contamination ; Vibrio parahaemolyticus ; Vibrio cholerae
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: E-8.1-E-8.6
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  • 23
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Weber, L., Armenteros, M., Soule, M. K., Longnecker, K., Kujawinski, E. B., & Apprill, A. Extracellular reef metabolites across the protected Jardines de la Reina, Cuba Reef System. Frontiers in Marine Science, 7, (2020): 582161, https://doi.org/10.3389/fmars.2020.582161.
    Description: Coral reef ecosystems are incredibly diverse marine biomes that rely on nutrient cycling by microorganisms to sustain high productivity in generally oligotrophic regions of the ocean. Understanding the composition of extracellular reef metabolites in seawater, the small organic molecules that serve as the currency for microorganisms, may provide insight into benthic-pelagic coupling as well as the complexity of nutrient cycling in coral reef ecosystems. Jardines de la Reina (JR), Cuba is an ideal environment to examine extracellular metabolites across protected and high-quality reefs. Here, we used liquid chromatography mass spectrometry (LC-MS) to quantify specific known metabolites of interest (targeted metabolomics approach) and to survey trends in metabolite feature composition (untargeted metabolomics approach) from surface and reef depth (6 – 14 m) seawater overlying nine forereef sites in JR. We found that untargeted metabolite feature composition was surprisingly similar between reef depth and surface seawater, corresponding with other biogeochemical and physicochemical measurements and suggesting that environmental conditions were largely homogenous across forereefs within JR. Additionally, we quantified 32 of 53 detected metabolites using the targeted approach, including amino acids, nucleosides, vitamins, and other metabolic intermediates. Two of the quantified metabolites, riboflavin and xanthosine, displayed interesting trends by depth. Riboflavin concentrations were higher in reef depth compared to surface seawater, suggesting that riboflavin may be produced by reef organisms at depth and degraded in the surface through photochemical oxidation. Xanthosine concentrations were significantly higher in surface reef seawater. 5′-methylthioadenosine (MTA) concentrations increased significantly within the central region of the archipelago, displaying biogeographic patterns that warrant further investigation. Here we lay the groundwork for future investigations of variations in metabolite composition across reefs, sources and sinks of reef metabolites, and changes in metabolites over environmental, temporal, and reef health gradients.
    Description: This work was supported by the Dalio Foundation (now “OceanX”) and the National Science Foundation (OCE-1736288) (award to Amy Apprill). The mass spectrometry samples were analyzed at the WHOI FT-MS Users’ Facility with instrumentation funded by the National Science Foundation (grant OCE-1058448 to EK and MK) and the Simons Foundation (Award ID #509042, EK). Lastly, a portion of the publication fees was supported by the Massachusetts Institute of Technology (MIT) Open Access Article Publication Subvention fund from MIT Libraries.
    Keywords: Metabolomics ; Coral reefs ; Microorganisms ; Ecology ; DOM cycling
    Repository Name: Woods Hole Open Access Server
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  • 24
    Publication Date: 2022-01-04
    Description: Abstract
    Description: Existing methodologies for estimating woody aboveground biomass and carbon stored therein have been developed for forests but are not tailored to the vast dryland ecosystems where vegetation is heterogenous and highly disturbed. Still, those methods are widely applied with questionable results and possible problematic implications, not only for biomass quantification but also for disturbance ecology, biodiversity research, and ecosystem service assessments. We hereby propose a new methodology especially designed to encompass small, disturbed, and irregular woody growth while keeping sampling effort within reasonable limits. Meaningful demographic growth classes are deployed which enable a stratified sampling design and structure a practicable workflow for integration of different allometric models. To account for the high natural and anthropogenic disturbance levels typically shaping dryland vegetation, our method incorporates a detailed damage assessment by harnessing the ecological archive contained in trees. This allows for quantification of biomass losses to certain disturbance agents, uncovers interactive effects between disturbance agents, and enables assessing the impact of disturbance regime shifts. Extrapolation of biomass losses to stand or landscape level also greatly improves the usual reference state comparison approach. Here, we review the problems of conventional methodologies being applied to drylands, develop and present the improved method proposed by us, and perform a formal method comparison between the two. Results indicate that the conventional allometric method is systematically underestimating biomass and carbon storage in disturbed dryland ecosystems. The bias is highest where general biomass density is lowest and disturbance impacts are severest. Damage assessment demonstrates a dependency between main disturbance agents (elephants and fire) while generally biomass is decreased by increasing elephant densities. The method proposed by us is more time consuming than a conventional allometric approach, yet it can cover sufficient areas within reasonable timespans. Consequent higher data accuracy with concomitant applicability to a wider range of research questions are worth the effort. The proposed method can easily be attuned to other ecosystems or research questions, and elements of it may be adapted to fit alternative sampling schemes.
    Description: Other
    Description: This article is a preprint and has not been certified by peer review. The finally published paper can be accessed at: https://doi.org/10.1016/j.ecolind.2021.108466
    Keywords: Ecology ; Biota ; Biomass ; Carbon ; Carbon Storage Dynamics ; Conservation Areas ; Ecology ; Ecosystem ; National Park ; Vegetation ; Vegetation Structure ; Wildlife
    Type: Text , Text
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  • 25
    Publication Date: 2022-03-09
    Description: Abstract
    Description: Nature conservation and restoration in terrestrial ecosystems is often focused on increasing the numbers of megafauna, expecting them to have positive impacts on ecological self-regulation processes and biodiversity. In sub-Saharan Africa, conservation efforts also aspire to protect and enhance biodiversity with particular focus on elephants. However, elephant browsing carries the risk of woody biomass losses. In this context, little is known about how increasing elephant numbers affects carbon stocks in soils, including the subsoils. We hypothesized that (1) increasing numbers of elephants reduce tree biomass, and thus the amount of C stored therein, resulting (2) in a loss of soil organic carbon (SOC). If true, a negative carbon footprint could limit the sustainability of elephant conservation from a global carbon perspective. To test these hypotheses, we selected plots of low, medium, and high elephant densities in two national parks and adjacent conservancies in the Namibian component of the Kavango Zambezi Transfrontier Area (KAZA), and quantified carbon storage in both woody vegetation and soils (1 m). Analyses were supplemented by the assessment of soil carbon isotopic composition. We found that increasing elephant densities resulted in a loss of tree carbon storage by 6.4 t ha−1. However, and in contrast to our second hypothesis, SOC stocks increased by 4.7 t ha−1 with increasing elephant densities. These higher SOC stocks were mainly found in the topsoil (0–30 cm) and were largely due to the formation of SOC from woody biomass. A second carbon input source into the soils was megaherbivore dung, which contributed with 0.02–0.323 t C ha−1 year−1 to ecosystem carbon storage in the low and high elephant density plots, respectively. Consequently, increasing elephant density does not necessarily lead to a negative C footprint, as soil carbon sequestration and transient C storage in dung almost compensate for losses in tree biomass.The dataset contains the raw data of soil analyses up to 1 m soil depth and vegetation data on plot level. A third sheet of the excelfile contains necessary information about abbreviations used within the dataset.
    Keywords: Ecology ; Environment ; Carbon ; Soil Organic Carbon ; Conservation Areas ; Ecosystem ; Vegetation
    Type: Dataset , Dataset
    Format: MS Excel
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  • 26
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    Aquatic sciences 51 (1989), S. 108-128 
    ISSN: 1420-9055
    Keywords: Chemistry ; mountain lakes ; silica ; acidity ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 μeq 1−1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.
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  • 27
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    Aquatic sciences 51 (1989), S. 235-248 
    ISSN: 1420-9055
    Keywords: Ecology ; ciliates ; river ; water quality ; sphaerotilus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Since sewage treatment plants are most effective in Switzerland, the micro-benthic communities in receiving running waters have changed considerably. From January 1980 to September 1981 the periphyton communities in 13 Swiss streams and rivers were monthly investigated. The NH4-N concentration in these waters varied between 0.015 and 1.0 mg/l. Four typical communities of microorganisms were found: In unpolluted running waters mainly small vagile ciliates were abundant; in slightly polluted waters peritricha (in the presence of bacteria) were found; in moderatly polluted waters peritricha in combination of few hymenostomata and Sphaerotilus could grow when bacteria and some degredable organic material where present; in polluted waters the well-known Spaerotilus-community (after Liebmann) could be found. The microscopic as well as the macroscopic aspect should be considered to qualify the degree of pollution in streams and rivers.
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  • 28
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    Oecologia 79 (1989), S. 417-426 
    ISSN: 1432-1939
    Keywords: Demography ; Ecology ; Frugivory ; Seed dispersal ; Tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Fruit-eating animals deposit viable seeds in patterns that determine the conditions under which seeds and seedlings live or die. Many tree species are scatter-dispersed by birds, bats, or other small frugivores that regurgitate, defecate, or drop seeds singly or in pairs. These scatterdispersed plant species normally recruit as isolated individuals, and are unlikely to evolve exceptional resistance to herbivores, pathogens, or to other sources of density-dependent seed or seedling mortality. Other tree species are clump-dispersed by larger terrestrial or arboreal frugivores that defecate seeds in masses which produce bouquets of seedlings. Because their seeds invariably germinate in close proximity to other seedlings, clump-dispersed species necessarily evolve chemical or mechanical defenses against seed predators, pathogens, and herbivores that act in a densitydependent manner. Population and genetic attributes should reflect this basic dichotomy in the conditions of seedling recruitment. I predict that seedlings of scatter-dispersed species rarely survive near parents or in dense aggregations under frugivore roosts. Seed dispersal should be mandatory, often to light gaps or other special habitats. Outbred adults and juveniles are expected to exist at low densities in loose aggregations or random distributions. Seedlings of clump-dispersed trees are pre-adapted for survival in dense aggregations near parents, as well as in fecal clumps. Substantial recruitment of juveniles and young adults should occur from undispersed seeds under and near parent trees. Such species should be common, highly aggregated, and show strong genetic family structure. Because recruitment requires dispersal, scatter-dispersed plant species should be especially vulnerable to loss of dispersal agents. Because offspring consistently recruit near parents, clump-dispersed plants should be less vulnerable to temporary loss of dispersal agents.
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  • 29
    ISSN: 1432-1939
    Keywords: Phacophyta ; Inorganic carbon assimilation ; Carbonic anhydrase ; Carbon dioxide compensation concentration ; Ecology ; Taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Characteristics of inorganic carbon assimilation by photosynthesis in seawater were investigated in six species of the Fucales (five Fucaceae, one Cystoseiraceae) and four species of the Laminariales (three Laminariaceae, one Alariaceae) from Arbroath, Scotland. All of the algae tested could photosynthesise faster at high external pH values than the uncatalysed conversion of HCO 3 - to CO2 can occur, i.e. can “use” external HCO 3 - . They all had detectable extracellular carbonic anhydrase activity, suggesting that HCO 3 - use could involve catalysis of external CO2 production, a view supported to some extent by experiments with an inhibitor of carbonic anhydrase. All of the algae tested had CO2 compensation concentrations at pH 8 which were lower than would be expected from diffusive entry of CO2 supplying RUBISCO as the initial carboxylase, consistent with the operation of energized entry of HCO 3 - and / or CO2 acting as a “CO2 concentrating mechanism”. Quantitative differences among the algae examined were noted with respect to characteristics of inorganic C assimilation. The most obvious distinction was between the eulittoral Fucaceae, which are emersed for part of, or most of, the tidal cycle, and the other three families (Cystoseiraceae, Laminariaceae, Alariaceae) whose representatives are essentially continually submersed. The Fucaceae examined are able to photosynthesise at high pH values, and have lower CO2 compensation concentrations, and lower K1/2 values for inorganic C use in photosynthesis, at pH 8, than the other algae tested. Furthermore, the Fucaceae are essentially saturated with inorganic C for photosynthesis at the normal seawater concentration at pH 8 and 10°C. These characteristics are consistent with the dominant role of a “CO2 concentrating mechanism” in CO2 acquisition by these plants. Other species tested have characteristcs which suggest a less effective HCO 3 - use and “CO2 concentrating mechanism”, with the Laminariaceae being the least effective; unlike the Fucaceae, photosynthesis by these algae is not saturated with inorganic C in normal seawater. Taxonomic and ecological implications of these results are considered in relation to related data in the literature.
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  • 30
    ISSN: 1432-1939
    Keywords: Logging disturbance ; Land gastropods ; Ecology ; Genetics ; Population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ecological and genetic properties of two North American terrestrial gastropods (Mesomphix spp.) were characterized in paired control and previously logged watersheds in two North Carolina forests (Coweeta and the Great Smoky Mountains National Park) of the Southern Appalachian Biosphere Reserve Cluster. Shell growth was greater in the control sites, but density and mortality were largely independent of prior logging history and forest reserve. Based on starch gel electrophoresis data, both species showed their highest levels of genetic diversity in the Coweeta forest, the component of the reserve cluster which had the most extensive and variable history of logging disturbance. M. subplanus also exhibited higher levels of heterozygosity in logged than in control watersheds, and M. andrewsae showed over twice as many rare alleles in disturbed sites as in control sites. F-statistic analysis depicted both excess levels of homozygosity and moderate genetic differentiation among the populations, reflecting the effects of small population size and perhaps drift and inbreeding. Estimated gene flow was relatively low. These results correspond to the recent finding by Bryant et al. (1987) and others on the effects of bottlenecks, and to the contrasting history of habitat instability of the two major study forests.
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  • 31
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    Environmental management 13 (1989), S. 43-54 
    ISSN: 1432-1009
    Keywords: Sustainable development ; Ecology ; Agroecosystems ; Field research ; Statistical reliability ; Southeast Asia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Farmers attempting to subsist in tropical uplands often rely upon unsustainable resource use practices that lead to soil erosion, declining crop yields, and a loss of soil productivity capacity. Other uses of tropical uplands, including logging and conversion of forest to rangelands, have similar results. The undesirable effects of these actions are felt on-site, at the watershed level, and even nationally. Ecological cause-effect relationships are poorly understood, and few examples exist of the successful integration of ecological knowledge with upland development. It is hypothesized that recent results of ecological research could be applied to uplands management so that stable sustainable systems of human use may be established. A second hypothesis is that statistically reliable data can be obtained from experiments in upland situations, although natural variations of soils, weather, and vegetation are great. To test these hypotheses, research involving multinational collaboration among American and Southeast Asian scientists has begun. The objective of the work is to provide credible quantitative information to help policy and decision makers and resident farmers to plan and implement improved practices based on ecological principles. Some findings to date include: 1. Ecological principles are difficult to relate to the practical context of upland agroecosystems. Indeed, the null hypothesis is necessary for planning experiments and demonstrations. 2. The “signal-to-noise” ratio in these field experiments is low, and the detection of changes due to human intervention in soil erosion, nutrient movement, and plant productivity is difficult. 3. Obstacles to field research in developing countries include logistic, cultural, political, and institutional factors. It is essential that local land managers participate from the start with scientific researchers in designing experiments. 4. Planned collaboration among academic and government scientists facilitates design of relevant research and the implementation of results. 5. The idea of ecologically based management has been well received by researchers and government officials in Asia. There is little argument with the logic of the approach. 6. Pressures for quick responses to urgent problems in the uplands conflict with the need for careful, long-term, statistically valid scientific research. 7. Ecological principles are vaguely understood and poorly articulated in the scientific literature. The transfer and application of ecological science to the developing world would be enhanced by clearer statements of principles.
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  • 32
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    Environmental management 13 (1989), S. 425-433 
    ISSN: 1432-1009
    Keywords: Interdisciplinarity ; Small islands ; Aeolian project ; Ecology ; Economy ; Human factors ; Environmental research methodology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Environmental research is characterized in each of its successive phases by a strong interdisciplinarity. A rotational groups system (RGS) method is proposed as an instrument to encourage interaction among researchers from fields that are traditionally far apart. Meetings conducted with the RGS procedure involve all the researchers, who, in repeated and topical encounters, are able to exchange information on a wide variety of environmental subjects. These meetings can be arranged according to a special calendar, through a series of phases treating different aspects of the same subjects to be discussed, and above all, referring to specific “themes” and “working guidelines” organized on the basis of criteria designed to favor an exchange of ideas and constructive discussion. At the end, the plenary assembly edits an overall resume of the proceedings, and votes on the final resolution, which brings together all the conclusive opinions regarding the themes discussed.
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  • 33
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    Environmental biology of fishes 25 (1989), S. 187-193 
    ISSN: 1573-5133
    Keywords: Foraging ; Ethology ; Ecology ; Chaetodontid ; Territorial ; Corallivore ; Corals ; Reef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The chevron butterflyfish,Chaetodon trifascialis, is found throughout the Indo-Pacific. It is a territorial, diurnal, corallivore found in close association withAcropora spp. corals. The feeding behavior of 33 individuals was studied over six seasons in three habitats.Chaetodon trifascialis spent one third of its active time feeding. However, there was much individual variation. Fish had significantly higher feeding rates during the early afternoon, and there were no significant differences in the feeding rates between the seasons. Feeding rates were significantly different between the three habitats. TheMontipora-rich habitat had the highest feeding rates (x = 10.74 bites min-1 ± 0.87, all corals combined) and theAcropora-Montipora mixed habitat had the lowest feeding rates (x = 4.58 bites min-1 ± 0.63, all corals combined). Females fed significantly more than males. WhileC. trifascialis had been thought to only eatAcropora spp. corals, it occasionally fed onMontipora spp. andPocillopora sp. corals whenAcropora spp. were scarce.Chaetodon trifascialis exhibited patterns predicted by foraging theory of an energy maximizer. Territory sizes were inversely related to food density and feeding rates were inversely related to intruder rates. This is a promising system for future testing of foraging strategy models.
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  • 34
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In this part properties and efficiency of the developed model1,2 are discussed. A variation of the parameters shows that vigorous effects are caused by the effective aggregation. All calculations show that at low conversion there are little temporal steps between the sequential aggregation steps. In the range of 5% to 20% conversion the velocity of aggregation decreases and the aggregative stability agrees with experiences given in the literature. It is shown that the calculated results are in agreement with the experimental results and therefore the presented model is a suitable possibility to describe the formation of some PVC-morphology properties.
    Notes: In der vorliegenden Arbeit werden die Eigenschaften des früher1,2 entwickelten Modells untersucht und diskutiert. Die Variation der Modellparameter zeigt einen großen Einfluß der Aggregationsprozesse auf die Subkornmorphologie. Bei niedrigen Monomerumsätzen ist das Zeitintervall zwischen zwei aufeinanderfolgenden Aggregationsschritten sehr klein, so daß für das Teilchenwachstum die Geschwindigkeit der Aggregation der Unterstrukturen entscheidend ist. Im Bereich zwischen 5% und 20% Monomerumsatz sinkt die Aggregationsgeschwindigkeit sehr stark, so daß für das Teilchenwachstum zunehmend die Polymerisationsreaktion an Bedeutung gewinnt. Aggregative Stabilität wird nach dem Modell für einen Teilchengrößenbereich erhalten, der sich in Übereinstimmung mit experimentellen Daten aus der Fachliteratur befindet. Die berechneten Teilchengrößen entsprechen ebenfalls den in der Literatur publizierten experimentellen Werten, so daß das Modell eine gute Grundlage für die Beschreibung einiger morphologisch bestimmter Polymereigenschaften bildet.
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  • 35
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    Angewandte Makromolekulare Chemie 165 (1989), S. 21-34 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden unidirektionale Verbundwerkstoffe aus Novolakharz mit Kohlenstoff-Fasern gemäß der Prepreg-Methode verarbeitet. Das Novolakharz wurde durch Polymerisation von Phenol mit Formaldehyd (Mol-Verhältnis 1 : 0,82) und Oxalsäure als Katalysator (1,5 Gew.-% von Phenol) hergestellt. Die Härtung des Novolakharzes wurde mit Hexamethylentetramin (Hexa) durchgeführt, während das geeignete Verhältnis durch die IR-Spektroskopie bestimmt wurde.Es wurden Proben aus Novolak/Hexa (Gew.-Verhältnis 14: 1), verstärkt mit kommerziellen Kohlenstoff-Fasern, unter verschiedenen Bedingungen (z. B. verschiedene thermische Programme und verschiedene Verhältnisse von Novolakharz : Kohlenstoff-Fasern) hergestellt. Die mechanischen Eigenschaften der hergestellten Proben (wie Biegefestigkeit, Zugfestigkeit, usw.) wurden bestimmt, und ihre Struktur wurde mit Hilfe der Elektronenmikroskopie untersucht.Mit zunehmendem Volumenverhältnis der Kohlenstoff-Fasern werden nicht nur alle mechanischen Eigenschaften des verstärkten Materials verbessert, sondern auch sein Nutzungsgrad nimmt zu, und die Herstellungsbedingungen üben einen größeren Einfluß aus. Die mit dem gleichen Verhältnis von Kohlenstoff-Fasern (z. B. 15 Vol.-%) hergestellten Proben weisen mit zunehmendem Härtungsgrad des Novolaks verbesserte mechanische Eigenschaften auf. Der Häirtungsgrad des Novolaks während der Anfangsphase (Gel-Zeit) als auch während der Endphase (Nachhärtung) kann mit Hilfe der IR-Spektren des härtenden Novolaks verfolgt werden, während der Härtungsgrad der Zwischenphase nur indirekt aus den Werten der mechanischen Eigenschaften der entsprechenden Proben bestimmt werden kann.Aus der Korrelation zwischen den Herstellungsparametern und den mechanischen Eigenschaften der Proben ergeben sich optimale Bedingungen für die Verarbeitung in der Wärmepresse zur Herstellung von mit Kohlenstoff-Fasern verstärkten Novolakharzen (1. Phase: T1 = 125-145°C, t1 = 20 min - 1 h, ohne Druck; 2. Phase: T2 = 180-195°C, t2 = 40 min, P2 ≃ 1,5 kN /cm2).
    Notes: Unidirectional composite materials of novolac resin with carbon fibers were fabricated according to the prepreg method. Novolac resin was prepared by polymerization of phenol with formaldehyde (mole ratio 1 : 0.82) in the presence of oxalic acid as catalyst (1.5 wt.-% to phenol). The curing of novolac resin was performed with hexamethylenetetramine (hexa), while the appropriate proportion was determined by using the IR-spectroscopy.Specimens of novolac/hexa (weight ratio 14:1) reinforced with carbon fibers commercially available were fabricated under different conditions (e.g. different thermal programs and different proportions of novolac/carbon fibers). The mechanical properties of the fabricated specimens (like flexural strength, tensile strength, etc.) were determined and their structure was examined by scanning electron microscopy.By increasing the volume proportion of carbon fibers, not only all mechanical properties of the composite material were increased, but also their degree of utilization was increased and also the production conditions had greater influence. Concerning the specimens produced by the same proportion of carbon fibers (e.g. 15 vol.-%) their mechanical properties were improved by increasing the curing of novolac. The degree of curing of novolac during the initial phase (gel time) and during the ultimate phase (post-curing) can be followed with the aid of IR-spectra of the cured resin, while the degree of curing for the intermediate phase can be obtained only indirectly from the values of the mechanical properties of the corresponding specimens.From the correlation between the production parameters and the mechanical properties of the samples the optimal conditions for processing of the thermopress for the manufacture of carbon fiber reinforced novolac were concluded (1. phase: T1 = 125-145°C, t1 = 20 min - 1 h, without pressure; 2. phase: T2 = 180-195°C, t2 = 40 min, P2 ≃ 1,5 kN/cm2).
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  • 36
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    Angewandte Makromolekulare Chemie 165 (1989), S. 69-78 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In dieser Arbeit interessieren wir uns für den Einfluß von Konzentration und Temperatur auf den elektrischen Widerstand eines Butyl-Kautschuks (IIR), der mit zwei Typen von Ruß (Hoch-Abrasion-Schmelzofen-Ruß (HAF) und Schnell-Extrusion-Hochofen-Ruß (FEF)) versetzt ist. Ergebnis war, daß die Leitfähigkeit bei niedrigem Rußgehalt hauptsächlich durch thermische Aktivierung der Ladungsträger erreicht wird. Bei mittleren Konzentrationen überwiegt der Tunnel-Mechanismus bei niedriger Temperatur, gefolgt von der thermischen Aktivierung bei relativ hoher Temperatur. Dies gilt für beide Rußarten. Das metallartige Verhalten bei Gemischen mit hoher Rußkonzentration kann sowohl der thermischen Ausdehnung der Tunnelwege zwischen Kohlenstoff-Agglomeraten als auch dem Zusammenbruch der Kohlenstoff-Agglomerate bei steigender Temperatur zugeschrieben werden.
    Notes: In this study we are interested in the effect of concentration and temperature on the electrical resistivity of butyl rubber (IIR) loaded with two types of carbon black, (namely, high abrasion furnace black (HAF), and fast extrusion furnace black (FEF)). It was found that the conductivity at low carbon black concentrations is mainly achieved by thermal activation of carriers. Tunneling mechanism at low termperature followed by thermal activation at relatively high temperature is found to be predominant for moderate concentrations for both carbon blacks. The metal-like behaviour which was observed in highly loaded compounds was attributed to both, the thermal expansion of the tunneling paths between carbon-carbon agglomerates and the breakdown of carbon agglomerates with temperature.
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  • 37
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    Angewandte Makromolekulare Chemie 165 (1989), S. 79-87 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Arbeit beschreibt die Synthese von Halogenderivaten des Phenylglycidylethers und die Möglichkeiten der Verwendung von diesen Komponenten als Flammverzögerer und reaktive Verdünnungsmittel für Epoxidharze.Mit Hilfe der Nelder-Mead-Simplexmethode wurden die besten Reaktionsbedingungen gefunden. Die so hergestellten Produkte zeichnen sich durch eine hohe Qualität aus und wurden mit einem niedermolekularen Epoxidharz gemischt und mit Diaminodiphenylmethan gehärtet.Die Viskosität von Harzgemischen und die Brennbarkeit der gehärteten Systeme wurden untersucht. Mit dem erhöhten Gehalt an Halogen (Chlor oder Brom) steigt die Viskosität, und die Brennbarkeit der Epoxide wird reduziert.
    Notes: This study deals with the synthesis of halogenated derivatives of phenyl glycidyl ether and with possibilities of their use as flame retardants and reactive diluents of epoxy resin.The best reaction conditions optimized by Nelder-Mead simplex method were found. The products of very high quality were prepared. They were mixed with a lowmolecular epoxy resin and cured by diamino diphenyl methane.The viscosity of the resin mixtures and limiting oxygen index of cured systems were determined. It was found that a higher content of halogen, both chlorine and bromine, causes increasing viscosity and reduced flammability of the epoxides.
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  • 38
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Messungen von Tg, Tm und Tc (Trübungspunkt) wurden Phasendiagramme der vier verträglichen Polymermischungen von chlorierten isotaktischen Polypropylenen (Chlorgehalt 39,2 (CPP-40) und 49,8 Gew.-% (CPP-50)) mit Poly(ethylen-co-vinylacetat)en (Vinylacetatgehalt 40 (EVA-40) und 45 Gew.-% (EVA-45)) untersucht. Von den vier Mischungspaaren war die Mischung von CPP-50 mit EVA-40 am besten verträglich.
    Notes: By measuring Tg, Tm and Tc (cloud point) phase diagrams for the four miscible blends of chlorinated isotactic polypropylenes (chlorine content 39.2 (CPP-40) and 49.8 wt.-% (CP-50)) with Poly(ethylene-co-vinyl acetate)s (vinyl acetate contents 40 (EVA-40) and 45 wt.-% (EVA-45)) were investigated. The blend of CPP-50 with EVA-40 was the most compatible of the four blend pairs.
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  • 39
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Synthese und Charakterisierung von Kationenaustauschmembranen aus PE-PS-DVB-Interpolymeren für die Elektrolyse von Borax-Lösung zur Erzeugung von Borsäure und Natronlauge wurden durchgeführt und mit den Eigenschaften von im Handel erhältlichen Membranen („Nafion 324“ und „Permaplex C-20“) verglichen.
    Notes: The synthesis and the characterization of the PE-PS-DVB interpolymer cationexchange membranes in the electrolysis of borax solutions to produce boric acid and sodium hydroxide simultaneously was carried out. The characterization of the teflon based “Nafion 324” and polystyrene-DVB based “Permaplex C-20” membranes was also performed in the same system for comparison.The DVB contents were varied between 3 - 12% (by wt. in total monomers) and the increase of the cross-links resulted in the decrease of the water contents and ionexchange capacities of the membranes. The PE present in the membrane acted as a barrier for electroosmotic water transport. The membranes with high DVB contents showed better electrolysis performance due to their low water contents and low electroosmotic water transport properties. The use of the interpolymer membrane containing 11.6% DVB resulted in high current efficiency and high sodium cation dynamic transport number and worked satisfactorily at the process conditions of borax electrolysis.
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  • 40
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 165 (1989), S. 125-131 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Rizinusöl und difunktionellen Säuren, wie Oxal-, Malon-, Bernstein-, Glutar-, Adipin-, Suberin- und Sebacinsäure, wurden Prepolyester hergestellt. Diese Prepolyester (PPE) wurden anschließend mit Methylmethacrylat und 1% Ethylenglykoldimethacrylat als Vernetzer interpenetriert. Die Polymerisation wurde radikalisch mit Benzoylperoxid gestartet. Die neuen PPE/Polymethylmethacrylat (PMMA)-interpenetrierenden Netzwerke wurden als Pulver erhalten. Sie wurden durch ihr Löseverhalten, IR-Spektroskopie und ihr thermisches Verhalten charakterisiert.
    Notes: Prepolyesters were obtained from castor oil and dibasic acids, viz oxalic, malonic, succinic, glutaric, adipic, suberic and sebacic acid. These prepolyesters (PPE) were subsequently interpenetrated with methyl methacrylate containing 1% ethylene glycol dimethacrylate as crosslinker by radical polymerization initiated with benzoyl peroxide. The novel PPE poly(methyl methacrylate) PPE/PMMA interpenetrating polymer networks (IPNs) were obtained as powder. They were characterized by solubility behaviour, IR spectral study and thermal behaviour.
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  • 41
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 2,4-Ionen, ein polymeres quartäres Ammoniumsalz, wurde auf einem makroporösen chlormethylierten Poly(Styrol-co-Divinylbenzol)-Harz (XAD-2) immobilisiert. Der Ionen-Gehalt des Harzes, der durch CHN-Elementaranalyse bestimmt wurde, betrug 50,2 g/kg Harz. Der wichtigste Nebeneffekt des modifizierten Harzes, das Ausbluten des Katalysators 2,4-Ionen, kann durch eine spektrophotometrische Methode, die extrem geringe Konzentraionen an freiem Ionen an der Oberfläche des Harzes messen kann, ermittelt werden.Die Aktivität der immobilisierten 2,4-Ionen/Kobalt(II)-phthalocyanin-tetranatriumsulfonat-Komplexe in bezug auf die oxidative Kupplung von Thiolen ist viel niedriger als im homogenen Fall, aber noch beträchtlich höher als im polymerfreien System. Die beobachtete Abnahme der Reaktionsgeschwindigkeit resultiert nicht aus Behinderungen des Massentransports, sondern vorzugsweise aus den Katalysatoreigenschaften wie z. B. einem sehr niedrigen N+/Co-VerhtUtnis. Die aktiven Zentren scheinen nur in der äußeren Hiille der Harzpartikel vorhanden zu sein.
    Notes: A poly(quaternary ammonium) salt, 2,4-ionene, has been immobilized on a macroporous chloromethylated poly(styrene-divinylbenzene) resin (XAD-2). The ionene content of the resin, determined by CHN elemental analysis, was 50.2 g/kg resin. The most important side effect of the modified resin, catalyst (2,4-ionene) bleeding, can be detected by a spectrophotometric method capable of determining extremely low concentrations of free ionene in the supernatant of the resin.The activity of these immobilized 2,4-ionene/cobalt(II)phthalocyanine-tetrasodiumsulfonate (CoTSPc) complexes towards the oxidative coupling of thiols is much lower than in the homogeneous case, but still considerably higher than for the polymer free system. The observed decrease in reaction rate does not originate from the considerable mass transfer resistances but predominantly from catalyst properties like a very low local N+/Co ratio. The active sites appear to be present in the outer shell of the resin particles only.
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  • 42
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Röntgendiffraktometrische Untersuchungen und DSC-Messungen an Blend-Filmen, die aus Lösungen von PEEK und PES hergestellt wurden, zeigen eine Phasenseparation bei den Filmen, die bei 340°C hergestellt wurden. Das Kristallisationsverhalten von Filmen, die bei 340°C hergestellt, anschließend abgeschreckt und bei 180°C getempert wurden, ist identisch mit dem von PEEK. Filme, die bei 300°C hergestellt wurden, kristallisierten erst durch Tempern bei 250°C. Blockcopolymere, die aus Oligomeren von PEEK und PES erhalten wurden, unterscheiden sich in dieser Hinsicht von Blends der gleichen Zusammensetzung. Die Glastemperatur von Copolymeren mit einem PEEK-Gehalt von mehr als 50% liegt höher als die von PEEK selbst, während der Schmelzpunkt dieser Copolymeren niedriger als der von PEEK ist.
    Notes: Polymer blends of PEEK with PES were prepared by the solution blending method. Copolymers composed of PEEK and PES components were synthesized from these oligomers. The formation conditions exerted an influence over the molecular aggregation and the crystallization behaviors of the blend films and block copolymers which were examined by X-ray diffractometry and DSC analysis. As a result, phase-separation in the blend films was found when the formation temperature was high. The blend films formed at 340°C, quenched and annealed at 180°C, exhibited the same crystallization behavior as those of PEEK. In the case of the blend films formed at 300°C, the annealing of the films at 250°C was required to crystallize the blend films. The Tg of a copolymer with a PEEK component content of more than 50% tends to shift toward a higher temperature than the Tg of PEEK itself, and the Tm of the copolymer toward a lower temperature than that of PEEK ist.
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  • 43
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 129-134 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Reaktionsprodukt eines Cyclohexanon-Formaldehyd-Harzes mit dem Säurechlorid des Radikalinitiators 4,4′-Azo-bis(4-cyanopentansäure) wurde als Initiator für die Styrolpolymerisation eingesetzt, um ein Cyclohexanon-Formaldehyd-Harz/Polystyrol-Copolymeres zu bilden. Das Copolymere zeigte ähnliche Löslichkeit wie Polystyrol.
    Notes: The reaction product of cyclohexanone-formaldehyde resin with an acid chloride of a radical initiator, 4,4′-azo-bis(4-cyano pentanoic acid) was used as initiator for styrene polymerization to form a cyclohexanone-formaldehyde resin/polystyrene copolymer. The copolymer showed similar solubility as polystyrene.
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  • 44
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 145-155 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Entgegengesetzte Ladungen wurden durch tertiäre Amin- und Carboxylgruppen in Polyurethan (PU) und Polystyrol (PS) eingeführt, um durch gemeinsame Massepolymerisation ein interpenetrierendes PU/PS Polymernetzwerk (IPN) zu erhalten. Vier IPNs wurden hergestellt: ein Voll-IPN, zwei Semi-IPNs und ein lineares Blend. Die Wirkung der geladenen Gruppen auf die mechanischen Eigenschaften und die Morphologie der vier Polymermischungen wurde untersucht.Es wurde gefunden, daß PU/PS IPNs mit geladenen Gruppen keine Phasenseparation und somit homogene Verteilung aufweisen, was durch elektronenmikroskopische (SEM) Aufnahmen nachgewiesen wurde. Dynamisch-mechanische Messungen zeigen, daß die Übergangspeaks des Verlust-Moduls E″ in die Mitte zwischen den beiden Übergangspeaks der beiden Komponenten ohne geladene Gruppen liegen. Dies ist von der Zunahme des Gehaltes an geladenen Gruppen abhängig. Gleichzeitig nimmt der Speichermodul E′ in einer Stufe ab, was im Gegensatz zu der zweistufigen Abnahme bei Proben ohne Ladungsträger steht.Die Zugfestigkeit nimmt in allen vier Polymermischungen mit der Zunahme an Acrylsäure (AA) in Poly(Styrol-Acrylsäue) PSAA zu, was in dem PU/PSAA Voll-IPN besonders deutlich wird.
    Notes: Opposite charges, namely tertiary amine and carboxyl groups, were introduced into polyurethane (PU) and polystyrene (PS), respectively, to prepare PU/PS interpenetrating polymer networks (IPNs) by means of simultaneous bulk polymerization. Four IPNs were synthesized: a full-IPN, two semi-IPNs and a linear blend. The effect of charge groups on the mechanical properties and morphology of the four polymer alloys was investigated.It is found that the PU/PS IPN which was incorporated with charge groups is free of any phase-separation, and sufficiently uniformly distributed, as can be seen from the corresponding scanning electron microscopy (SEM) photographs. Dynamic mechanical analysis indicates that the transition peak of the loss modulus E″ will move towards the centre between the two transition peaks of both components in the absence of charge groups, as a function of an increase in the contents of the opposite charge groups. Meanwhile the storage modulus E′ will decrease in a single-stage way from the previous two-stage mode.The tensile strength in all the four polymer alloys increased markedly along with an increase in the contents of acrylic acid (AA) in the poly(styrene-acrylic acid) (PSAA), which clearly can be seen for the PU/PSAA full-IPN.
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  • 45
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 157-168 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Pyrolysis behaviour and coke characteristics of different precursors for carbon processing: thermosetting resins (resol, novolak), hydrolytic lignin, pitch, tar as well as their blends were studied using differential thermal analysis (DTA) and X-ray diffraction techniques. The blends novolak-pitch, resol-tar and resol-hydrolytic lignin show a higher coke yield after carbonisation up to 1000°C compared to the corresponding individual substances. A good correlation between the integral procedural decomposition temperature T*A of the investigated precursors and their coke yield is found.
    Notes: Mittels Thermo- und Röntgenstrukturanalyse wird eine vergleichende Untersuchung des Pyrolysevorganges und der Mikrostruktur des aus zwei Gruppen organischer Bindemittel und deren Mischungen gewonnenen Koksrückstandes durchgeführt. Gruppe I umfaßt reine und mit Hydrolyselignin gefüllte Resol- und Novolak-Phenol-Formaldehydharze und Gruppe II Steinkohlenpech und -teer. Es wird festgestellt, daß sich die Mischungen Novolakharz-Pech, Resolharz-Teer und Resolharz-Hydrolyselignin beim Erhitzen nicht wie mechanische Gemische verhalten und eine erhöhte Ausbeute an Koksrückstand liefern. Weiterhin wird gefunden, daß die integrale Endtemperatur der Pyrolyse (T*A) dieser Substanzen als quantitatives Maß für die Ausbeute an Koksrückstand im Anschluß an die Carbonisierung der Proben dienen kann.
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  • 46
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 217-223 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The paper describes the successful synthesis of silicon containing bismaleimide resin 4,4′-carbo(4,4′-bismaleimido phenoxy)diphenyl silane. The char yield of the bismaleimide resin in N2 atmosphere was found to be 55% at 800°C. Chain extension of bismaleimide with 4,4′-diamino diphenyl sulfone reduced the char yield and thermal stability.
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  • 47
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: As hard blocks in polyether block amides, polyamides are used whose length is intensively regulated by dicarboxylic acids. Since, with regard to melting and crystallization behaviour, this acid constitutes an interfering structural unit in the chain, and in the case of a completely converted product each chain contains one acid molecule, it is essential to know where in the chain incorporation will occur. As opposed to monofunctional chain regulators which always form a chain end, a bifunctional chain regulator can a priori also be randomly incorporated into the inner part of the chain. This leads to a far greater interference than occurs if the chain regulator molecule and the chain end, which acts as an interfering unit in any case, coincide with each other.By means of adipic acid-regulated oligoamides based on lauryl lactam, the incorporation of the chain regulator was examined by NMR spectroscopy and compared with model calculations. This resulted in a close match only if it was presupposed that the incorporation was carried out randomly with the same degree of probability at any point whatsoever between two lauryl lactam structural units or at the chain end.Further calculations illustrate the effects of the incorporation of the chain regulator on the size of the amorphous portion.
    Notes: Als Hartblöcke in Polyetherblockamiden werden durch Dicarbonsäuren stark geregelte Polyamide eingesetzt. Da die Säure in Hinblick auf das Schmelz- und Kristallisationsverhalten einen Störbaustein in der Kette darstellt und bei einem ausgeregelten Produkt jede Kette ein Säuremolekül enthält, ist es von Bedeutung zu wissen, wo in der Kette der Einbau erfolgt. Anders als bei monofunktionellen Reglern, wo der Regler stets ein Kettenende bildet, kann ein bifunktioneller Regler a priori auch statistisch im Inneren der Kette eingebaut werden. Dies führt zu einer viel stärkeren Störung, als wenn das Reglermolekül und das sowieso als Störstelle wirkende Kettenende zusammenfallen. Anhand adipinsäuregeregelter Oligoamide auf Basis von Laurinlactam wird kernresonanzspektroskopisch der Einbau des Reglers untersucht und mit Rechnungen verglichen. Es ergibt sich nur dann gute Übereinstimmung, wenn vorausgesetzt wird, daß der Einbau statistisch erfolgt und dabei mit gleicher Wahrscheinlichkeit für jede beliebige Stelle zwischen zwei Laurinlactambausteinen oder am Kettenende abläuft. Weitere Rechnungen verdeutlichen den Einfluß des Reglereinbaus auf die Größe des amorphen Anteils.
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  • 48
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Auf Grund von mikroskopischen Beobachtungen wurde festgestellt, daß unter dem Einfluß von UV-Strahlung die Oberfläche von PVC-Filmen einer Formveränderung unterliegt. Auf der Oberfläche erscheinen Bläschen und Löcher. Die sich absondernden Gasprodukte der Polymerfotodestruktion verursachen die Bildung dieser Bläschen und Löcher. Größere Oberflächenänderungen wurden in Filmen mit einem Zusatz von 1-5% eines MMA/MA-Copolymeren beobachtet. Das weist auf eine in diesem Modifikator stattfindende Photoabbaureaktion hin, deren Ergiebigkeit größer ist als in reinem PVC. Dieser Modifikator wird in PVC eingeführt, um die Filmoberfläche zu verbessern, beschleunigt allerdings ihre Zerstörung unter dem Einfluß von UV-Strahlung. Es wurde festgestellt, daß Cyclohexanonspuren in den Proben den Photoabbau von MMA/MA retardieren, diesen Prozeß in PVC aber beschleunigen.
    Notes: By means of microscopic observation, the deformation of the surface of PVC films caused by 253.7 nm UV radiation was investigated. Numerous blisters and holes were formed by the gaseous photodecomposition products of the polymer.More apparent deformation of the films containing MMA/MA suggests that the photodecomposition of this modifier occurs with higher efficiency than that of PVC.MMA/MA copolymer is introduced into PVC films to improve the smoothness of their surface, but this modifier accelerates the deformation of this surface under UV irradiation. It was also found that traces of cyclohexanone in samples retard the photodecomposition of MMA/MA and accelerate this process in PVC.
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  • 49
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 29-41 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Anzahl von Harzen wurde durch gemeinsame Kondensation von p-Aminoacetophenon (p-AAph), substituierten Benzoesäuren wie m-Tolylsäure (m-TA), o-Tolylsäure (o-TA), Phthalsäure (PhA), p-Nitrobenzoesäure (p-NBA), p-Chlorbenzoesäure (p-CIBA) und Formaldehyd (F) in Gegenwart von verschiedenen Säuren und Basen als Katalysatoren hergestellt. Die Harze wurden IR-spektroskopisch charakterisiert. Die Löslichkeitsparameter wurden gemäß Small's Gruppenbeteiligung berechnet; sie stimmen gut mit den experimentellen Werten überein. Das thermische Verhalten und die bakteriologischen Eigenschaften der Harze wurden auch untersucht.
    Notes: A number of resins has been prepared by condensing p-amino-acetophenone (p-AAph) with substituted benzoic acid such as m-toluic acid (m-TA), o-toluic acid (o-TA), phthalic acid (PhA), p-nitrobenzoic acid (p-NBA), p-chlorobenzoic acid (p-CIBA) and formaldehyde (F) in presence of some acids and bases as catalysts. The resins were characterized by infrared spectra of the characteristic groups. The solubility parameters were calculated from Small's group contribution which agreed well with the experimental values. The thermal behaviour and the bacteriological properties of the resins have also been investigated.
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  • 50
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Notwithstanding their more common beginnings, liquid crystals and molecular biology developed mainly parallel and independently during the last one hundred years.Molecule-phase relationships on the one and complex static-dynamic treatments on the other hand seem to forward mutually integrative views in our days.Biomesogen approaches will deepen our insights into the spatio-temporal coherences of biological systems. They might contribute significantly to the understanding of life processes.
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  • 51
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent studies on ionic distribution in solutions and in suspensions were reviewed. Suspensions of latex particles, which were large enough to be seen under an ultramicroscope, were investigated by the 2-D Fourier transformation. The micrograph showing ordered structures gave discrete scattering spots, whereas those of disordered arrangements displayed no spots or halos. The two-state structure gave a limited number of halo, confirming our previous conclusion that the very frequently observed single, broad scattering peak was reminiscent of some kind of ordering of solute species. By using an image data analyser, the crystallization process was shown to follow the Ostwald ripening mechanism. The concurrent study by the quasi elastic light scattering method and by the Fourier analysis gave consistent scattering profiles, which indicated that the ordering phenomena took place in the entire volume of suspensions. The scattering intensity (correctly the lattice factor) was calculated for cubic systems with paracrystalline distortion. The peak intensity was lowered by enhanced distortion, while the peak position itself was not affected. This justifies our previous treatment of the single, broad peak in terms of the Bragg equation. The experimentally found scattering curve was compared with this theoretical calculation; the degree of distortion was evaluated.
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  • 52
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Lyotropic liquid crystalline phases of cellulose derivatives were explored as an analytical tool. Molar mass dependent measurements of the helicoidal cholesteric pitch of a cellulose tricarbanilate/solvent system may be used to determine the molar mass of this derivative by optical means. The compatibility of a ternary liquid crystalline system can be adequately investigated by a study of the supermolecular structure with spectroscopic measurements.
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  • 53
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The application of carotenoids as natural additives in various water-based or water-compatible formulations for the pigmentation of foods and feeds is seriously hampered by their insolubility in aqueous systems.Therefore, in order to develop the full potential of colour strength and to achieve a high degree of bioavailability during gastro intestinal passage, the coarse crystalline material has to be transformed into a microdisperse state.Exemplified with β-carotene, a novel non-mechanical process is described that transforms the carotenoids into a colloidal hydrosol characterized by an average particle size of about 0.1 μm.The process is based on the preparation of a transient high temperature solute state of the carotenoid in a water-miscible solvent, coupled with succeeding rapid aqueous precipitation in the presence of a stabilizing polymer colloid. The obtained hydrosols are characterized by photon-correlation-spectroscopy(size), and microelectrophoresis(colloidal stabilization).The bioavailability was tested by monitoring plasma levels of β-carotene in veal calves.
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  • 54
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymer science is mature enough to allow one to think about tailor-making macromolecular compounds aimed at interacting purposely with living systems. Reasons for developing bioresorbable polymers for temporary therapeutic applications are discussed with respect to property adjustments and economical factors. The field of the applications is first described and guidelines for tailor-making multimeric macromolecules with desired properties are presented. The approach led to focuss investigations on poly(α-hydroxy acids) and functional poly(β-hydroxy acids) derived from natural hydroxy acids, namely lactic, glycolic and malic acids. Physical, mechanical and biological properties of some corresponding polymers and copolymers are presented. Last but not least, examples of applications currently investigated are recalled.
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  • 55
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When blood comes into contact with an artificial surface, a number of events occur which include protein adsorption, platelet activation and the activation of the intrinsic pathway of blood coagulation. With the increased application of blood containing artificial devices, there is a great demand to develop new biomaterials which retard thrombus formation. Our new approach to solving this problem is to mimic the non-thrombogenic surface of natural biological membranes at least in a simple form. We have developed a polymerisable phospholipid and polyesters based on the major phospholipid polar head group present on the erythrocyte outer membrane surface. The coagulation of blood exposed to these polymers was examined by the technique of Material Thrombelastography, a relatively simple test for the in vitro screening of polymer thrombogenicity. We present results which indicate that the polymerised phospholipid and polyesters show reduced thrombogenicity, and may therefore have potential for future biomaterials.
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  • 56
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: After implantation a stable bond between the implant and the surrounding tissue is required. Therefore a high cell adhesion of the polymer surface of the implant must be achieved. Depending on the treatment time of a polydimethylsiloxane foil with oxygen plasma, the cell adhesion can be improved. FT-IR spectroscopy and ESCA analysis were used to characterize the surface modification. The cell spreading and cell adhesion increase with increasing hydrophilic character of the polymer surface after plasma treatment. A pronounced correlation was found between the efficiency of DNA and protein content, characterizing cell growth, and the spreading of the cells.Polydimethylsiloxane, Glow-Discharge, Surface Modification, Cell Adhesion, Cell Proliferation.
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  • 57
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have used synthetic polymers as tools to probe endocytosis and lysosome function. Their particular value lies in their well-defined chemical constitution and in the possibility to custom-synthesize molecules with desired characteristics. Polyvinylpyrrolidone, Percoll and polystyrene beads have been 125I-labelled and used to explore the borderland of pinocytosis and phagocytosis. Derivatized poly(aspartamide), poly(hydroxypropylmethacrylamide) and a polylysine-poly(ethylene oxide) block copolymer have been used to investigate the effects of hydrophobic moieties and sugar residues on substrate-selection in pinocytosis. The effect of cationic moieties has been studied using vinylpyrrolidone-vinylamine copolymers.Poly(hydroxypropylmethacrylamide) with certain oligopeptide side---chains have been shown to be susceptible to lysosomal peptidases. Ethylene glycol oligomers are being used to study the basal permeability of the lysosome membrane.Soluble macromolecules have considerable potential in targeted drug-delivery. Drugs attached to appropriate polymers by covalent links that are susceptible to lysosomal enzymes can deliver drug to target cells and avoid unwanted sideeffects. Synthetic macromolecules have several advantages over their natural counterparts: they are chemically more robust, less immunogenic, and easier and cheaper to prepare in bulk.
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  • 58
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diagnostics are e. g. reagents or combinations of reagents or measure bloodcomponents down to concentrations of 10-15 mol/1 in reproducable form. To achieve this target diagnostics have to fullfill special requirements in purity, uniformity, producibility and reproducibility. These requirements are also valid for integrated polymers and plastics. Examples of the application of polymers and plastics in diagnostics are e. g. materials for the blood-plasma-separation, the stabilization of proteins, solid phases in immunoassays as reagent tubes, microtiterplates and latexparticles.Reciprocal actions between polymers, plastics, polymer additives, blood and bloodsubstances like proteins in diagnostic tests can be seen as indications to similar effects by the intracorporeal applications of plastics in surgery and in general for contacts of natural materials with plastics, as usual in the foodpacking.
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  • 59
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using Eupergit, a synthetic resin, as an example, the necessary characteristics of a support for high performance affinity chromatography (HPAC) are demonstrated. To such a support different ligands can be immobilized and used for the separation of biopolymers.From the range of possible applications a few examples are chosen. Immunoglobulins are isolated in one step by protein A-HPAC, the purified antibodies are immobilized and applied to immunoaffinity-HPLC for the isolation of corresponding antigens. Concanavalin A-HPAC of membrane proteins was chosen to represent chromatography with immobilized lectins. Antithrombin could be isolated from human plasma by the use of immobilized heparin. HPAC has the advantage of affinity chromatography, which is above all highly specific. As the support is resistant to high pressure and has well defined microparticles with a particular pore size, it provides a much higher yield at considerable flow rates. The handling of materials like this is simpler, the separation of the sample is quicker and can be reproduced more easily.
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  • 60
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    Angewandte Makromolekulare Chemie 166 (1989), S. 257-272 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Controlled polyelectrolyte adsorption can be used to render phospholipid bilayer membranes sensitive to physical and chemical signals. We describe in this paper the design and construction of macromolecular switches for bilayer membranes, which can be used to create lipid vesicles that release their contents rapidly and quantitatively in response to changes in pH, temperature, light intensity or glucose concentration. The kinetics and mechanisms of the molecular switching processes observed in such systems are also discussed.
    Notes: Kontrollierte Adsorption von Polyelektrolyten kann ein wirksames Werkzeug im Design von dünnen molekularen Filmen sein. Man kann erwarten, daß die Adsorption von Polyelektrolytketten das empfindliche Kräftegleichgewicht erheblich beeinflußt, das die strukturellen und funktionellen Eigenschaften von geordneten Strukturen wie Einzel-, Doppel- und Mehrfachschichten bestimmt. Andererseits ist die Adsorption von Polyelektrolyten außerordentlich sensitiv auf Umgebungsparameter, z.B. pH, Temperatur oder lonenstärke. Kontrollierte Adsorption kann daher zu Sensitivität auf bestimmte chemische oder physikalische Stimuli führen, sodaß auf diese Weise ein molekularer Schaltmechanismus entworfen werden kann. Durch Umsetzen dieser ldee in reale Systeme gelang es uns, molekulares Schalten in Mischungen von Poly(2-ethylacrylsäre) mit natürlichen oder synthetischen Phosphatidylcholinen zu bewirken. Insbesondere haben wir Phosphatidylcholinvesikel hergestellt, die ihren lnhalt nach einer Änderung von pH, Temperatur, Glukosekonzentration oder nach Bestrahlung mit Licht schnell und quantitativ freisetzen. Die Entwicklung und die Herstellung von Doppelschichtmembranen, die auf solche Änderungen reagieren, sowie die Kinetik und der Mechanismus des damit verbundenen molekularen Schaltprozesses werden im vorliegenden Artikel diskutiert.
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  • 61
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Enzymes can be immobilized by gel entrapment, by microencapsulation, by physical or ionic adsorption, by covalent binding to inorganic or organic carriers, or by whole cell immobilization. Of particular interest is the large number of chemical reactions developed for the covalent binding of enzymes via their nonessential functional groups to inorganic carriers such as glass, ceramics and iron, to natural polymers such as cellulose and Sepharose, and to synthetic polymers such as nylon, polyacrylamide, and other vinyl polymers and copolymers possessing reactive chemical groups. The stability of certain enzymes is markedly increased on their immobilization. It was thus possible to transform the biologically active polymer derivatives into active enzyme beads, enzyme capsules, enzyme columns and enzyme membranes and these enabled the construction of enzyme reactors such as the batch-stirred tank reactors, the continuous packed bed reactors, and fluidized bed reactors. So far mainly immobilized hydralases and isomerases are being used in industry on a large scale. It seems likely, however, that once adequate techniques become available for cofactor recycling, the use of immobilized enzymes will be extended to other organic reactions, particularly those involving stereospecific synthesis of simple or complex organic molecules. Among the industrial processes in which immobilized enzymes are being used, it is worth mentioning the industrial-scale continuous production of fructose enriched syrup from glucose by immobilized glucose-isomerase, the batch process for the production of 6-aminopenicillanic acid (6-APA) from penicillin G with the aid of immobilized penicillin amidase; the production of aspartame from aspartic acid and phenylalanine by immobilized thermoase; the large scale production of optically active amino acids with immobilized amino acid acylase; and the large scale production and application of immobilized lactase for the hydrolysis of lactose. The recently developed process for acrylamide production using immobilized nitrilase containing microbial cells should also be referred to. The successful use of an NAD-polyethylene glycol conjugate (NAD-PEG) as a nondialyzable water-soluble coenzyme derivative in the enzymic synthesis of leucine from α-ketoisocaproic acid and ammonia, in a membrane-enclosed reactor containing L-leucine dehydrogenase, NAD-PEG, formate and formate dehydrogenase, illustrates the new possibilities opened up by making use of cofactor-polymer conjugates. The use of enzyme-polymer conjugates in analytical and clinical is also illustrated.
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  • 62
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The genetic make-up of living systems especially of isolated cells can be altered by a variety of methods including chemical or light-induced mutation. More modern procedures are the in vitro recombination of nucleic acids and the cell-cell fusion.The new methods are especially useful to reprogram microorganisms to produce valuable proteins or other natural products in excess quantties. In the following we will elucidate the importance of the new techniques by describing the bacterial production of glucose dehydrogenase, of the proteinase inhibitor stefin A and by outlining the methods and promisses of substractive cloning. Although the economic value of genetic engineering techniques still awaits justification, the importance of the methodology for basic biological research is well documented.
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  • 63
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Immobilization of whole cells has become an efficient tool for biosynthesis, biotransformation and analysis. High cell density, high operational stability, easy handling, propably in continuous systems, and multiple reuse are important advantages of immobilized cells. In comparison to other methods like adsorption, crosslinking and encapsulation, the entrapment within a polymeric network is the most widely applied technique in heterogeneous biocatalysis. For immobilizing mammalian cells nearly exclusively the adsorption onto micorcarriers is used. Requirements for the polymers to be used in such immobilized cell systems are discussed in detail.
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  • 64
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    Angewandte Makromolekulare Chemie 168 (1989), S. 1-8 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Vier Pyridazinderivate wurden synthetisiert und als Beschleuniger für Naturkautschukmischungen entwickelt. Die rheologischen Eigenschaften wurden mit Hilfe eines Monsanto Rheometers 100 bestimmt. Die rheometrischen Daten wurden für die Berechnung der kinetischen Konstanten der Vulkanisationsreaktion in Anwesenheit der synthetisierten Verbindungen benutzt. Verglichen mit Mercaptobenzthiazol (MBT), einem Beschleuniger der häufig in der Kautschukindustrie eingesetzt wird, zeigten diese Verbindungen eine gute Beschleunigerwirksamkeit.
    Notes: Four pyridazine derivatives were synthesized and evaluated as accelerators in natural rubber (NR) mixes. The rheological characteristics were determined by a Monsanto Rheometer 100. The kinetic constants for the vulcanization reaction in the presence of the synthetic compounds were calculated using the rheometric data. The compounds showed a good accelerating efficiency compared with mercaptobenzothiazole (MBT), which is widely used in rubber industry.
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  • 65
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    Angewandte Makromolekulare Chemie 170 (1989), S. 173-182 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Ansammlung von als inaktiv angenommenen „Dimeren“ und „Trimeren“ sowie der Verbrauch von aktiven Spezies mit der Reaktionszeit im säurekatalysierten Furfurylalkohol (FA)/Formaldehyd (F) System wurde durch GPC-Technik unter Anwendung eines Doppeldetektors bewiesen.Ein Reaktionsmechanismus wurde für den Kondensationsprozeß vorgeschlagen, der einige Widersprüche der bisherigen Untersuchungen erklären kann.
    Notes: Accumulation of “dimers” and “trimers” considered to be inactive and consumption of active ones with reaction time in furfuryl-alcohol (FA)/formaldehyde (F) acid catalyzed condensation system was proved by GPC technique using double detector.A reaction mechanism was proposed for the condensation process explaining some contradictions of investigations collected so far.
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  • 66
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dieser Artikel befaßt sich mit silylierten bzw. maleinisierten Polybutadienölen und ihren Effekten in Kieselsäure und Silicate bzw. Kreide enthaltenden Kautschukmischungen. Sie erweisen sich als wirksame Hilfsstoffe für die Substitution von Ruß durch mineralische Füllstoffe.
    Notes: This paper deals with silylated and maleated polybutadiene oils and their effects in rubber compounds containing silica(tes) resp. chalk as fillers. They are shown to be efficient aids in the substitution of oil-dependent carbon black by mineral fillers.
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  • 67
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    Angewandte Makromolekulare Chemie 171 (1989), S. 79-89 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die isotherme und nichtisotherme Kristallisation von isotaktischem Polypropylen, das mit ausgewählten organischen Pigmenten gefärbt war, wurde mittels DSC untersucht. Es wurde gefunden, daß die Nukleierungsfähigkeit der Pigmente mit deren chemischem Aufbau und mit der Erniedrigung der freien Energie für den Keimbildungsprozeß verbunden ist. Die experimentellen Daten wurden mit Hilfe der bekannten Avrami-Gleichung analysiert.Blau-Pigment und Rot-Lack beschleunigen die Kristallisation von isotaktischem Polypropylen, während Orange-Pigment die Kristallisationsgeschwindigkeit etwas herabsetzt.
    Notes: The isothermal and non-isothermal crystallization of isotactic polypropylene coloured with selected organic pigments was examined by differential scanning calorimetry. It was found that the nucleating ability of pigments is connected with their chemical nature and with the reduction of the free energy for critical nucleus formation. The experimental data were analysed in terms of the well known Avrami equation.Blue pigment and Red lake are substances which accelerate the crystallization of isotactic polypropylene, while Orange pigment decreases the crystallization rate slightly.
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  • 68
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Um bei Kationen-Austauschmembranen eine dauerhafte Selektivität für die Durchlässigkeit von einwertigen Kationen zu erzielen, wurde eine Polyethylenimin-Schicht auf der Membranoberfläche durch Säureamidbindung zwischen Polyethylenimin und den —SO2Cl-Gruppen einer Styrol-co-Divinylbenzol-Membran erzeugt. Nach der Reaktion wurden die im Inneren der Membran verbleibenden —SO2Cl-Gruppen durch Tauchen in wäßrige Natronlauge hydrolysiert.Die so gewonnenen Kationen-Austauschmembranen wurden mittels Elektrodialyse von Seewasser hinsichtlich ihrer Selektivität für die Durchlässigkeit von einwertigen Kationen, ihres elektrischen Widerstandes, ihrer Stromleistung und ihrer überfüh-rungszahlen für Natrium-Ionen untersucht. ATR-IR-Messungen auf der Membran-oberfläche belegen, daß die Shäureamidbindung gegenüber starker Hydrolyseeinwirkung stabil war.
    Notes: In order to give the monovalent cation permselectivity to the cation exchange membrane permanently, polyethyleneimine layer was formed on the membrane surface by acid-amide bond between polyethyleneimine and the —SO2Cl groups of a styrene-divinylbenzene copolymer membrane. After the reaction, the —SO2Cl groups remaining in the inner part of the membrane were hydrolyzed by immersing the membrane into an aqueous sodium hydroxide solution.The resultant cation exchange membranes were evaluated by electrodialysis of sea water from the point of view of the monovalent cation permselectivity, electric resistance of the membrane, current efficiency, and transport number of sodium ions calculated by membrane potential in connection with reduced viscosity of the various commercial polyethyleneimines, ATR-IR measurements on the membrane surface suggested that the acid-amide bond was stable for severe hydrolysis reaction.
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  • 69
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    Angewandte Makromolekulare Chemie 171 (1989), S. 141-152 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Epoxidgruppen eines Copolymeren, das man durch Pfropfung von 2,3-Epoxypropylmethacrylat auf isotaktisches Polypropylen erhält, wurden mit niedermolekularen Carbonsäuren umgesetzt. Die Reaktion verläuft in Gegenwart von organischen Lösungsmitteln heterogen und kann durch tertiäre Amine beschleunigt werden. Die Geschwindigkeitskonstanten der Reaktion werden mit der Dissoziationskonstanten der gebundenen Säure und mit der Art des verwendeten Beschleunigers korreliert. Die Reaktivität der polymergebundenen Epoxidgruppen ändert sich im Vergleich mit Reaktionen unter homogenen Bedingungen nicht.
    Notes: Epoxy groups on isotactic polypropylene, to which 2,3-epoxypropylmethacrylate was grafted, were reacted with low molecular carboxylic acids. The reaction proceeds under heterogeneous conditions in the presence of organic solvents and it may be catalysed by tertiary amines. The rate constants of this reaction are correlated with the dissociation constant of the bonded acid and with the character of the used catalyst. The reactivity of polymer-bonded epoxy groups is not changed when comparing with reactions performed under homogeneous conditions.
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  • 70
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird eine neue Methode zur Einführung von hydrophilen Polyetherseitenketten in segmentierte Polyurethane unter Verwendung eines Polypropylenoxid-Macromeren mit 1,3-Diol-Gruppen an einem Kettenende, die als Kettenverlängerer fungieren, beschrieben. In diesem Prozeß wird eine Seitenkette quantitativ und direkt in medizinische Polyurethanelastomere eingebaut. Diese Entwicklung ist auch für Biowerkstoffe in künstlichen Organen von Interesse.
    Notes: A new method of introducing a hydrophilic polyether side chain into segmented polyurethane using a polypropylene oxide macromer with 1,3-diol at one chain-end, which behaves as chain extender, is described. In this procedure, a molecular-designed side-chain is incorporated quantitatively and directly into polyurethane biomedical elastomer. The design is also of interest to biomaterials in artificial organs.
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  • 71
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    Angewandte Makromolekulare Chemie 172 (1989), S. 233-233 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 72
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    Angewandte Makromolekulare Chemie 173 (1989), S. 85-100 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Orientierungsmechanismus von kaltverstrecktem, teilkristallinem Polyoxymethylen wurde durch Messung der Intensität der Weitwinkel-Röntgenstreuung (WAXS) untersucht. Die Anisotropie der Proben wurde im einachsigen Zugversuch bei etwa 130°C im Temperaturbereich zwischen Glasübergangstemperatur und Schmelzpunkt erzeugt. Der Prozess der plastischen Deformation wurde für verschiedene Stadien der Verstreckung diskutiert. Die Orientierungsverteilung der Kristalllamellen wurde qualitativ charakterisiert durch die Berechnung von Polfiguren aus den WAXS Streuintensitätsdaten. Der Grad der Orientierung wurde durch die Berechnung des Orientierungsfaktors für den [100] Flächennormalenvektor der Einheitszelle beschrieben. Die Textur der eingeschnürten Proben mit hoher Orientierung wurde als Mischung von axialer und uniplanar-axialer Textur erkannt. Als mögliche Erklärung für diesen Orientierungstyp wird ein Einfluß der Probengeometrie angenommen.
    Notes: The orientation mechanism of cold-drawn, partially crystalline polyoxymethylene (ULTRAFORM) samples was studied by performing wide angle X-ray scattering (WAXS) measurements. The anisotropic samples were prepared in uniaxial tensile tests around 130°C, in a temperature range between the glass transition and the melting point. The process of the plastic deformation is discussed for different degrees of anisotropy. The orientation distribution of the crystalline lamellae was qualitatively characterized by performing pole figure intensity calculations from the measured WAXS intensities. The degree of orientation was quantitatively described by calculating the orientation factors for the [100] normal vector of the unit cell. The texture of the necked samples with high orientation degrees was a mixture of axial and uniplanar-axial textures. An explanation for the formation of this kind of orientation is proposed assuming an influence of the sample geometry on the orientation process.
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  • 73
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    Angewandte Makromolekulare Chemie 173 (1989), S. 205-212 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Herkömmliches Vernetzen von Polyethylen niedriger Dichte (LDPE) wurde mit Dicumylperoxid (DCP) als Vernetzer durchgeführt. DCP wurde in verschiedenen Konzentrationen mit LDPE-Schnitzeln in einem Extruder bei 135 - 145°C gemischt. Monofilamentfäden wurden bei 110°C auf einer Laborziehmaschine gezogen. Die Zugdehnungseigenschaften, der prozentuale Schrumpf und die Dichte wurden mit Zunahme der DCP-Konzentration und der Heizdauer verbessert, während jedoch die prozentuale Quellung abnahm.
    Notes: Conventional crosslinking of low density polyethylene (LDPE) was carried out using dicumyl peroxide (DCP) as crosslinking agent. DCP in various concentrations was mixed with LDPE chips in an extruder at 135 - 145°C. Monofilaments were drawn on a laboratory drawing machine at 110°C. It was found that tensile properties, percent shrinkage and density were improved with the increase in the concentration of DCP and in the heating period, whereas, however, the percent swelling decreased.
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  • 74
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Resultate von Untersuchungen über die chemische Wechselwirkung zwischen einigen monofunktionellen Modellverbindungen, die die Struktur und Reaktivität von wärmehärtbaren Phenol- und Harnstoff-Formaldehyd-Harzen simulieren, mit Holzkomponenten (Hemicellulosen, Cellulose und Lignin) werden dargelegt. Während Hemicellulosen deutlich dazu neigen, Kondensationsprodukte mit diesen Modellverbindungen zu ergeben, reagieren Lignine in manchen Fällen weniger leicht und abhängig davon, durch welchen Prozeß sie gewonnen worden sind, und abhängig von der Art der Modellverbindung. Cellulose reagierte wegen ihrer Kristallinität nicht unter den gegebenen Bedingungen.
    Notes: Results are presented on the chemical interactions occurring when some monofunctional model compounds simulating the structure and reactivity of thermosetting phenol- and urea-formaldehyde resins are mixed with wood components (hemicelluloses, cellulose, and lignins). Whereas hemicelluloses clearly show a propensity to give condensation products with these model compounds, lignins can react less readily in some instances depending on the delignification procedure used to isolate them and on the type of model compound. Cellulose did not react under the conditions chosen, mostly because of its crystalline character.
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  • 75
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    Angewandte Makromolekulare Chemie 173 (1989), S. 183-193 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: XPS-, SSIMS- und Wasserkontaktwinkelmessungen wurden verwendet, um den chemischen Einfluß von CF4/O2-Entladungen auf Polycarbonat (PC) aus Bisphenol A zu charakterisieren. Die durch Plasmabehandlung erzeugte Oberflächenmodifizierung kann auf der Basis der im Plasma vorhandenen aktiven Spezies, deren Konzentration durch Actinometrie bestimmt worden ist, erklärt werden.Bei kleinen Gehalten an O2 im Gas (1%) tritt eine umfassende Fluorierung der Oberfläche bedingt durch die Pfropfung von Fluorkohlenstoff-Radikalen ein. Es werden perfluorierte Inseln gebildet, wie der hohe Wert des zunehmenden Kontaktwinkels zeigt. Bei 20-80% O2 reagieren Fluoratome mit der Oberfläche und ätzen sie teilweise. Kleine Gehalte an Fluor, aber keine perfluorierten Inseln werden beobachtet. Sauerstoff trägt zum Ätzen bei und oxidiert die PC-Oberfläche. Die Sauerstoffkonzentration auf der Oberfläche nimmt mit Zunahme des O2-Gehalts im Gas zu, ebenso die Bildung von stark oxidierten Inselchen auf der Probenoberfläche, wie die dramatische Abnahme der Kontaktwinkel zeigt. Eine Verminderung der Aromatizität der Oberfläche, die mit Hilfe von XPS und SSIMS beobachtet wird, ist die Folge dieser Reaktionen.
    Notes: XPS, SSIMS and water contact angle measurements have been used to characterize the chemical effect of CF4/O2 discharges on polycarbonate (PC) made from bisphenol A. We found that the surface modification induced by plasma treatment can be clearly explained on the basis of the acitve species present in the plasma, whose concentration has been studied by actinometry.With very low amounts of O2 in the gas feed (1%) extensive fluorination of the surface occurs, due to grafting of the fluorocarbon radicals. Perfluorinated islands are formed, as shown by the high value of advancing contact angles. In the 20-80% O2 range, fluorine atoms react with the surface, partially inducing etching. Low amounts of fluorine are observed on the sample and no perfluorinated islands. Oxygen participates in etching and oxidizes the PC surface. We observed an increase of the surface concentration of oxygen with increasing the O2 amount in the gas feed and also the formation of strongly oxidized islets on the sample surface, as shown by the dramatic reduction of receding contact angles. A reduction of surface aromaticity, observed by XPS and SSIMS, is the consequence of these reactions.
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  • 76
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    Angewandte Makromolekulare Chemie 173 (1989), S. 213-218 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An attempt was made to obtain cationic cellulose derivatives of highest possible degrees of substitution by treating dissolving grade pulps under homogeneous conditions with glycidyltrimethylammonium chloride in the solvent system dimethylacetamide/lithiumchloride. The influence of temperature, reaction time and molar ratio of the reagents was examined. A reaction time of 8 h and a temperature of 70°C have been found to be optimal. The cellulose content in solution and the molar ratio of the reagents have to be adapted to the used pulp.
    Notes: Es wurde der Versuch unternommen, durch Umsetzung von Zellstoffen mit Glycidyltrimethylammoniumchlorid im Lösungsmittelsystem Dimethylacetamid/Lithiumchlorid kationische Cellulosederivate mit möglichst hohen Substitutionsgraden zu erhalten. Hierzu wurden Temperaturabhängigkeit, Reaktionsdauer und Molverhältnis der Reaktanden untersucht. Als optimal erwies sich eine Reaktionsdauer von 8 h bei einer Reaktionstemperatur von 70°C. Der Cellulosegehalt in Lösung und das Molverhältnis der Reaktanden müssen dem verwendeten Zellstoff angepaßt werden.
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  • 77
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    Biopolymers 28 (1989), S. 773-781 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A second example of insertion of a water molecule into the helical backbone of an apolar peptide is presented here and compared to a similar occurrence in a longer peptide with the same type of sequence of residues, i.e., Boc-Aib-(Ala-Leu-Aib)3-OMe. The backbone of the title compound assumes an approximate 310-helical form with three 4 → 1 hydrogen bonds. In the place of a fourth 4 → 1 hydrogen bond, a water molecule is inserted between O(1) and N(4), and acts as a bridge by forming hydrogen bonds N(4) … W(1) (2.95 Å) and W(1) … O(1) (2.81 Å). The water molecule participates in a third hydrogen bond with a neighboring peptide molecule, W(1) … O(4) (2.91 Å). The insertion of the water molecule causes the apolar peptide to mimic an amphiphilic helix. Crystals grown from ethyl acetate/petroleum ether (reported here) or from methanol/water solution are in space group P212121 with a = 12.024(4) Å, b = 15.714(6) Å, c = 21.411(7) Å, Z = 4 and dcalc = 1.124 g/cm3 for C32H58N6O9 · H2O. The overall agreement factor R is 6.3% for 2707 reflections observed with intensities 〉 3σ(F) and the resolution is 0.90 Å.
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  • 78
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical shifts of base and H1′ protons of the single-stranded hexamers d(ATTACC) and d(GGTAAT), of the 1 : 1 mixtures of these complementary hexamers, and of the self-complementary dodecamer d(ATTACCGGTAAT) were measured at various temperatures in aqueous solution. Four different sample concentrations were used in the case of the dodecamer and of the mixture of the complementary hexamers; the individual hexamers were measured at two different DNA concentrations. Absorbance temperature profiles at five different NaCl concentrations were measured for the dodecamer in order to quantify the effect of the ionic strength on the duplex formation.Under suitable conditions of nucleotide concentration, temperature, and ionic strength, the dodecamer adopts either a B-DNA duplex or a hairpin-loop structure. Chemical shift vs temperature profiles, constructed for all samples, were used to obtain thermodynamic parameters either for the various stacking interactions in the single strands or for the duplex or the hairpin-loop formation. In the analysis of the duplex formation of the hexamers, a two-state approach appeared too simple, because systematic deviations were revealed. Therefore, a new three-state model (DUPSTAK) was developed. In order to investigate the magnitude of error arising from the use of the two-state approach in cases where the DUPSTAK model appears more appropriate, a series of test calculations was made. The magnitude of error in the enthalpy and in the entropy of duplex melting is found to depend linearly upon the actual melting temperature and not upon the individual ΔHOd and ΔSOd values.Thermodynamic analysis of the chemical shift vs temperature profiles in D2O solution (no added salt) yields an average Tmd value of 341 K (1M DNA) and ΔHOd of -121 kJ · mol-1 for the dimer/random-coil transition of the hexamer duplex d(ATTACC) · d(GGTAAT). For the duplex ⇄ random-coil transition of the 12-mer d(ATTACCGGTAAT) an average Tmd value of 336 K (1M DNA) and ΔHOd of -372 kJ · mol-1 are found. The hairpin/random-coil transition of d(ATTACCGGTAAT) is characterized by a rather large ΔHOh value, -130 kJ · mol-1, and an average Tmh value of 304 K.
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  • 79
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational method is elaborated for studying the water environment around regular polynucleotide duplexes; it allows rigorous structural information on the hydration shell of DNA to be obtained. The crucial aspect of this Monte Carlo simulation is the use of periodical boundary conditions. The output data consists of local maxima of water density in the space near the DNA molecule and the properties of one- and two-membered water bridges as function of pairs of polar groups of DNA.In the present paper the results for poly(dG) · poly(dC) and poly(dG-dC) · poly(dG-dC) are presented. The differences in their hydration shells are of a purely structural nature and are caused by the symmetry of the polar groups of the polymers under study, the symmetry being reflected by the hydration shell.The homopolymer duplex hydration shell mirrors the mononucleotide repeat. The water molecules contacting the polynucleotide in the minor groove are located nearly in the plane midway between the planes of successive base pairs. One water molecule per base pair forms a water bridge facing two polar groups of bases from adjacent base pairs and on different strands making a “spine”-like structure. In contrast, the major groove hydration is stabilized exclusively by two-membered water bridges; the water molecules deepest in the groove are concentrated near the plane of the corresponding base pair.The alternating polymer is characterized by a marked dyad symmetry of the hydration shell corresponding to the axis between two successive base pairs. The minor groove hydration of the dCpdG step resembles the characteristic features of the homopolymer, but the bridge between the O2 oxygens of the other base-stacking type is formed by two water molecules. The major groove hydration is characterized by high probability of one-membered water bridges and by localization of a water molecule on the dyad axis of the dGpdC step.The found structural elements are discussed as reasonable invariants of a dynamic hydration shell.
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  • 80
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    Biopolymers 28 (1989) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 81
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report dynamic light scattering measurements over a wide range of scattering vectors for fractionated samples of porcine submaxillary mucin (PSM) glycoproteins in two different solvents: 0.1M NaCl, and 6M GdnHCl. The relaxation spectrum has been successfully resolved into a slow mode corresponding to pure translational diffusion and a fast mode containing information on the relaxation times for intramolecular motion. Analysis of the slow mode permits a light scattering evaluation of the polydispersity of these high molecular weight mucin glycoprotein fractions. Determination of the longest intramolecular relaxation times τ1 shows that these are much longer for the PSM fractions in 0.1M NaCl compared to 6M GdnHCl. These data are consistent with earlier studies showing that the chain conformation is the same in both solvents, but that in 0.1M NaCl, the PSM glycoprotein undergoes a self-association process that is end-to-end in nature. Since the τ1 value is intimately related to the viscoelastic behavior of PSM solutions and gels, it is interesting to speculate that the end-to-end association process may be physiologically important.
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  • 82
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    Biopolymers 28 (1989), S. 835-849 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical computations are performed of the intercalative binding to a model d(CpG)2 minihelix of 7-H pyrido[4.3C]carbazole, the precursor of the antitumor bisintercalating drug ditercalinium. The conformations of the intercalation site are generated by the AGNAS procedure (algorithm to generate nucleic acid structures) of Miller and co-workers. The ligand-nucleotide interactions and the nucleotide conformational energies are computed with the SIBFA procedures (sum of interactions between fragments ab intio computed), which use formulas of empirical origin that reproduce ab initio SCF (self-consistent field) computations. Among the candidate intercalation sites most favored energetically, one has a pattern of conformational angles related to the one determined crystallographically by Sobell et al. in a series of x-ray structural studies of small intercalator-dinucleotide monophosphate complexes. Optimal values of the unwinding angle, found in the range of -12° to -14°, are consistent with available experimental data on DNA.
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  • 83
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of concanavalin A (Con A) on the thermotropic behavior of positively charged, glycosyl-free lipids and their mixtures with zwitterionic lipids was investigated by differential scanning calorimetry.The gel to liquid-crystal phase transition enthalpy of pure dipalmitoylcholine (DPC) was found to be significantly increased in the presence of Con A (ΔH = 31.2 and 42.5 KJ mol-1 lipid in the presence and in absence of Con A, respectively). Addition of the lectin to DPC liposomes, furthermore, induces the appearance of a new phase transition centered at 320 K. These results are interpretable by a partial hydrophobic interdigitation of the lectin molecule into the liposomal bilayer.The effect of Con A on the phase behavior of three 2:1 mixtures of zwitterionic and of positively charged lipids was also investigated. Phase diagrams of the systems dipalmitoylphosphatidylcholine-dihydrosphingosine (DPPC-DHS), sphingomyelin-dipalmitoylcholine (SPM-DPC), and dimyristoylphosphatidylcholine-dipalmitoylcholine (DMPC-DPC) are presented. In lipid mixtures of limited miscibility (DPPC-DHS and SPM-DPC), Con A induces pronounced phase-separation effects. These effects are attributable to a direct hydrophobic interaction of the lectin with the liposomal bilayer and do not require the presence of specific receptor groups.The possible relationship between lectin-induced phase separations in the lipid matrix of biomembranes, and the observed changes in membrane permeability, membranal enzymatic activities, etc., is briefly discussed.
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  • 84
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Two-dimensional nuclear Overhauser enhancement (2D NOESY) data are reported for the polypentapeptide of elastin, poly(VPGVG), and the cyclopentadecapeptide, cyclo(VPGVG)3. In both, the repeating type II Pro2-Gly3 β-turn can be derived from the NOE data, providing confirmation of many previous studies. In addition, other through-space connectivities are detailed that also compare favorably with previously determined crystal and solution structures for cyclo(VPGVG)3. Also, near identical data for the cyclopentadecapeptide and the polypentapeptide demonstrate the cyclic conformation-linear (helical) conformational correlate relationship between the two molecules. The 2D NOESY experiment is seen to be an effective means of establishing the presence or absence of a conformational relationship between a cyclic repeating sequence and its higher molecular weight linear counterpart. This is an approach of substantial practical value when developing the conformation of sequential polypeptides and when attempting to identify the presence of the conformation of a repeating peptide sequence within a more complex primary structure.Having established the basic conformational relationship between a cyclic conformation and its linear helical counterpart, cross peaks present in the linear helical structure that are not present in the cyclic conformational correlate can provide information on the interactions between adjacent turns of the helix. In this connection, a ValγCH3 ↔ ProβCH2 interaction is reported that can be the basis for determining the number of pentamers per turn of helix once it is determined whether it is dominantly the Val1 or Val4γCH3 that is interacting with the Pro2βCH2.
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  • 85
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    Biopolymers 28 (1989), S. 901-905 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
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  • 86
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    Biopolymers 28 (1989), S. 965-973 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligo-DNAs are synthesized on a solid support using the 9-fluorenylmethyloxycarbonyl group as a 5′-OH base labile protection. The synthesis of the pure protected nucleotides, a relevant phosphoramidite-type strategy of coupling, and the optimization of the deprotection steps are described. This new synthetic method is an alternative to the standard protocol that avoids acidic conditions.
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  • 87
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have applied the formalism developed previously for the kinetics of domain-localized reaction [S. Mazur and M. T. Record, Jr. (1986) Biopolymers 25, 985-1008] to describe complex mechanisms of association of a protein with a specific site on a large DNA molecule also containing many nonspecific binding sites. These nonspecific sites participate in the mechanism of formation of the specific complex through competitive binding and the facilitating mechanisms of sliding and transfer. The effects of localizing the sites in a domain are represented by a simple algebraic expression, and the sequence of interactions within the domain are described by equations closely related to a conventional, homogeneous solution mechanism. We apply this formalism to examine the interplay between sliding and direct transfer in domain-localized interactions in general and in the lac repressor-lac operator interaction in particular. Experimental investigation of the effect of the molecular location of the specific site (e.g., end vs middle of the polymer chain) on the kinetics of association may allow the contributions of sliding and direct transfer to be resolved.
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  • 88
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    Biopolymers 28 (1989), S. 975-993 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrostatic potentials around DNA are obtained by solving the nonlinear Poisson-Boltzmann (PB) equation. The detailed charge distribution of the DNA and the different polarizabilities of the macromolecule and solvent are included explicitly in the calculations. The PB equation is solved using extensions of a finite difference approach applied previously to proteins. Electrical potentials and ion concentrations are compared to those obtained with simpler models. It is found that the shape of the dielectric boundary between the macromolecule and solvent has significant effects on the calculated potentials near the surface, particularly in the grooves. Sequence-specific patterns are found, the most surprising result being the existence of positive regions of potential near the bases in both the major and minor grooves. The effect of solvent and ionic atmosphere screening of phosphate-phosphate repulsions is studied, and an effective dielectric function, appropriate for molecular mechanics simulations, is derived.
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  • 89
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    Biopolymers 28 (1989), S. 1019-1030 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have used Raman scattering to study the water O-H stretching modes at ∼ 3450 and ∼ 3220 cm-1 in DNA films as a function of relative humidity (r.h.). The intensity of the 3220-cm-1 band vanishes as the r.h. is decreased from 98% to around 80%, which indicates that the hydrogen-bond network of water is disrupted in the primary hydration shell (which therefore cannot have an “ice-like” structure). The number of water molecules in the primary hydration shell was determined from the intensity of the ∼ 3200-cm-1 band as about 30 water molecules per nucleotide pair. The ∼ 3400-cm-1 O-H stretch band was used for determining the total water content, and this band persists at 0% r.h., implying that 5-6 tightly bound water molecules per nucleotide pair remain. The frequency of the ∼ 3400-cm-1 O-H stretch mode is lower by 30 to 45 cm-1 in the primary hydration shell compared to free water. The water content as a function of r.h. obtained from these experiments agrees with gravimetric measurements. The disappearance of the ∼ 3200-cm-1 band and the shift of the ∼ 3400-cm-1 O-H stretch band provide a reliable way of measuring the hydration number of DNA.
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  • 90
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An estimation of the thermodynamic effects of a charged random coil, which is attached either to the N- or C-terminus of polyalanine, upon α-helix stability is attempted. A temperature-induced helix-coil transition of Ala20Lys20Phe and Lys20Ala20Phe was studied under various conditions of salt concentration and pH. By combining the results with previous ones for Ala20Glu20Phe and Glu20Ala20Phe, which have opposite electric charges to the present system [S. Ihara et al. (1982) Biopolymers 21, 131-145], the free energy of the coil to helix transition of the polyalanine block could be separated into two terms - one term for the electrostatic interaction of electric charges in the random-coil block with the α-helix dipole, and a second term for the intrinsic stability of the helix. The first term indicates the significance of the helix dipole-charge interactions, which affects the helix stability depending on the attaching side of the charged block and on the sign of the charges. This clearly shows the anisotropic stability of the α-helix. Furthermore, analysis of the dependence of these thermodynamic quantities on salt concentrations showed, assuming that the effect of the attached electric charges was symmetric (in other words, the absolute values of the electrostatic interaction terms were independent of the sign of electric charges), that the intrinsic stability of the α-helix was dependent on which side of the helix was attached to the random coil: a random coil attached to the N-terminus of the α-helix had little effect while that attached to a C-terminal significantly destabilized the helix.
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  • 91
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    Biopolymers 28 (1989), S. 1043-1058 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The velocity and orientation of T4 and λ DNA have been measured for the first 20 s during pulsed-field gel electrophoresis in order to clarify the DNA motions that occur. For a square pulse with field strength E = 10 V/cm, the velocity of λ DNA increases gradually to 10.5 μm/s in 1.0 s, declines to 8.6 μm/s, and then rises to a plateau value of 9.3 μm/s after 4 s. T4 DNA behaves similarly, but more slowly. Parallel measurements of fluorescence-detected linear dichroism show that the DNA becomes substantially aligned with its chain axis parallel to the electrophoretic field E after the pulse is applied. The alignment also shows an overshoot, an undershoot, and a plateau comparable to those seen for velocity. When the field strength increases, both the velocity and the alignment reach their peaks more quickly. For all field strengths and both molecular weights, the velocity peak occurs when the molecular center of mass has moved 0.3 to 0.5 L, where L is the chain contour length. A qualitative model is provided.
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  • 92
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    Biopolymers 28 (1989), S. 1059-1095 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the context of dynamic Monte Carlo simulations on a model protein confined to a tetrahedral lattice, the interplay of protein size and tertiary structure, and the requirements for an all-or-none transition to a unique native state, are investigated. Small model proteins having a primary sequence consisting of a central bend neutral region flanked by two tails having an alternating hydrophobic/hydrophilic pattern of residues are seen to undergo a continuous transition to a β-hairpin collapsed state. On increasing the length of the tails, the β-hairpin structural motif is found to be in equilibrium with a four-member β-barrel. Further increase of the tail length results in the shift of the structural equilibrium to the four-member β-barrel. The random coil to β-barrel transition is of an all-or-none character, but while the central turn is always the desired native bend, the location of the turns involving the two external strands is variable. That is, β-barrels having the external stands that are two residues out of register are also observed in the transition region. Introduction into the primary sequence of two additional regions that are at the very least neutral toward turn formation produces an all-or-none transition to the unique, native, four-member β-barrel. Various factors that can augment the stability of the native conformation are explored. Overall, these folding simulations strongly indicate that the general rules of globular protein folding are rather robust - namely, one requires a general pattern of hydrophobic/hydrophilic residues that allow the protein to have a welldefined interior and exterior and the presence of regions in the amino acid sequence that at the very least are locally indifferent to turn formation. Since no site-specific interactions between hydrophobic and hydrophilic residues are required to produce a unique four-member β-barrel, these simulations strongly suggest that site specificity is involved in structural fine-tuning.
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  • 93
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    Biopolymers 28 (1989) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 94
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequence-specific photomodification of oligodeoxynucleotide pAGAGTATTGACTTA (“a target”) has been carried out with the aid of complementary fluorescent probes. Such a probe consisted of oligodeoxynucleotide pAATACTCT and a chromophore group attached to its 5′ end. Three different derivatives of ethidium bromide were used as a chromophore. The photomodification was induced by nitrogen laser radiation (337 nm, 15 MW /cm2). The irradiation induces the following photodamages: target cleavage at the specific binding site with a cutting off of the 8-mer from its 5′ end (yield up to 12%), formation of specific covalent adduct target-probe with a yield of 20-70%, and piperidine-sensitive target modifications with a 7-27% yield (for different chromophores). The total yield of specific photodamages of all kinds is 50-80%. The target cleavage and generation of piperidine-sensitive modifications are optically nonlinear processes. Piperidine treatment of the irradiated samples led to specific cleavage of the target with the yield up to 40%. All kinds of observed modifications are not influenced by high concentrations of free radical scavengers: 1.3M tBuOH and 10 mM cystamine. The pattern of cleavage indicates that the most probable position of the chromophore is between T8 and G9 of the target, i.e., the chromophore stacks on top of the last A · T base pair of the duplex. The aggregate of evidence is in agreement with the mechanism of nonlinear photomodification (the cleavage and generation of piperidine-sensitive modifications) based on the transfer of two-photon excitation energy from the chromophore to the target.
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  • 95
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    Biopolymers 28 (1989), S. 1179-1186 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The physiological importance of heparin is due to its strong interaction with bivalent counterions, especially Ca2+. A diffusional approach of this property is presented in this article: the observable is the self-diffusion coefficient of the counterions, as a function of the ratio of the polyelectrolyte over the added salt concentrations. All the results are in agreement with a simple “quasi-chemical model” in which two different states are assumed for the counterions: “free” or “bound.” The proportions of these two types of ions are calculated according to the distribution function of the counterions around the polyion. We assume that those of counterions located at a distance closer than a, the characteristic distance, are bound; the others are free. The ionic distribution function is evaluated by a numerical integration of a cell model Poisson-Boltzmann equation. Finally, this model leads to a very good agreement with the experimental results, if the radius of heparin polyion is assumed to be 6 and 10 Å.
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  • 96
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    Biopolymers 28 (1989), S. 1189-1193 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The calculated spectrum of longitudinal compressional waves on DNA polymer chains is shown to be in excellent agreement with recently performed inelastic neutron scattering measurements in hydrated, oriented DNA crystals. This opens up a previously unexplored frequency regime of DNA science and establishes the validity of the phonon extended wave description of DNA elementary excitations in this region.
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  • 97
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    Biopolymers 28 (1989), S. 1259-1269 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthetic peptide Gly-L-Ala-L-Phe (C14H19N3O4 · 2H2O; GAF) crystallizes in the monoclinic space group P21, with a = 5.879(1), b = 7.966(1), c = 17.754(2) Å, β = 95.14(2)°, Dx = 1.321 g cm-3, and Z = 2. The crystal structure was solved by direct methods using the program SHELXS-86 and refined to an R value of 0.031 for 1425 reflections (〉 3σ). The tripeptide exists as a zwitterion in the crystal and assumes a near α-helical backbone conformation with the following torsion angles: ψ1 = -147.8°; φ2, ψ2 = -71.2°, -33.4°; φ3 ψ3 = -78.3°, -43.3°. In this structure, one water molecule bridges the COO- and NH3+ terminii to complete a turn of an α-helix and another water molecule participates in head-to-tail intermolecular hydrogen bonding, so that the end result is a column of molecules that looks like an α-helix. Thus, the two water molecules of crystallization play a major role in stabilizing the near α-helical conformation of each tripeptide molecule and in elongating the helix throughout the crystal. An analysis of all protein sequences around regions containing a GAF fragment by Chou-Fasman's secondary structure prediction method showed that those regions are likely to assume an α-helical conformation with twice the probability they are likely to adopt a β-sheet conformation. It is conceivable that a GAF fragment may be a good part of the nucleation site for forming α-helical fragments in a polypeptide, with the aqueous medium playing a crucial role in maintaining such transient species.
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    Biopolymers 28 (1989), S. 1271-1285 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution conformation of [D-Ala2]-leucine enkephalin in its zwitterionic form in DMSO-d6 has been monitored by one- and two-dimensional proton magnetic resonance spectroscopy at 500 MHz. The resonances from the labile amide protons and the nonlabile protons have been assigned from the shift correlated spectroscopy. The chemical shift of the amide and C-α protons are found to vary with temperature but in opposite directions, except the C-α proton of the terminal tyrosine residue. This behaviour has been explained by the shifting of equilibrium between the zwitterionic and neutral forms of the [D-Ala2]-leucine enkephalin and probably conformational changes accompanying temperature variation. The low values of the temperature coefficients of leucine and glycine amide protons indicate that these protons are either intramolecularly hydrogen bonded or solvent shielded. The observation of sequential cross peaks in the nuclear Overhauser effect spectra obtained at various mixing times, τm (200-900 ms), indicate an extended backbone, which does not corroborate with the presence of a folded structure, i.e., β-bend type structure. The estimate of interproton distances in conjunction with the low values of temperature coefficients of the leucine and glycine amide protons and vicinal coupling constants 3JHN-CαH have been rationalized by the predominance of two γ-bends in the backbone conformation of [D-Ala2]-leucine enkephalin. The γ-bend around the D-Ala residue has Φ = 80° and ψ = 270°, while the one around Phe it has Φ = 285° and ψ = 90°.
    Additional Material: 9 Ill.
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  • 99
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    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1287-1294 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The peptide N-Boc-L-Gly-dehydro-Phe-NHCH3 was synthesized by the combination of N-Boc-L-Gly-dehydro-Phe azlactone and methylamine. The peptide crystallizes in orthorhombic space group P212121 with a = 5.679(2) Å, b = 16.423(9) Å, c = 19.198(10) Å, V = 1791(2) Å3, Z = 4, dm = 1.212(5) Mg m-3, dc = 1.237(1) Mg m-3. The structure was determined by direct methods using SHELXS 86. The structure was refined by full-matrix least squares procedure to an R value of 0.049 for 1509 observed reflections. The molecular dimensions are, in general, in good agreement with the standard values. The bond angle Cα-Cβ-Cγ in the dehydro-Phe residue is 133.6(5)°. The peptide backbone torsion angles are θ1 = -171.4(4)°, ω0 = 178.2(4)°, φ1 = -57.2(6)°, ψ1 = 141.2(4)°, ω1 = -174.4(4)°, φ2 = 71.5(6)°, ψ2 = 7.2(6)°, and ω2 = -179.8(5)°. These values show that the backbone adopts the β-bend type II conformation. The Boc group has a trans-trans conformation. The side-chain torsion angles in dehydro-Phe are χ2 = 1.6(9)°, χ22,1 = 0.5(9)°, and χ22,2 = 179.8(6)°. The plane of C2α-C2β-C2γ is rotated with respect to the plane of the phenyl ring at 0.5(6)°, which indicates that the atoms of the side chain of the dehydro-Phe residue are essentially coplanar. As a result of the β-bend in the structure, an intramolecular hydrogen bond is formed between the oxygen of the ith residue and the NH of the (i + 3)th residue at a distance of 2.940(5) Å. The crystal structure is stabilized by a network of hydrogen bonds and van der Waals interactions.
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  • 100
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 28 (1989) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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