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  • 1
    Publication Date: 2020-12-21
    Description: This paper introduces the three-dimensional Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), which treats atmospheric dynamics, radiation, and chemistry interactively for the height range from the earth’s surface to the thermosphere (approximately 250 km). It is based on the latest version of the ECHAM atmospheric general circulation model of the Max Planck Institute for Meteorology in Hamburg, Germany, which is extended to include important radiative and dynamical processes of the upper atmosphere and is coupled to a chemistry module containing 48 compounds. The model is applied to study the effects of natural and anthropogenic climate forcing on the atmosphere, represented, on the one hand, by the 11-yr solar cycle and, on the other hand, by a doubling of the present-day concentration of carbon dioxide. The numerical experiments are analyzed with the focus on the effects on temperature and chemical composition in the mesopause region. Results include a temperature response to the solar cycle by 2 to 10 K in the mesopause region with the largest values occurring slightly above the summer mesopause. Ozone in the secondary maximum increases by up to 20% for solar maximum conditions. Changes in winds are in general small. In the case of a doubling of carbon dioxide the simulation indicates a cooling of the atmosphere everywhere above the tropopause but by the smallest values around the mesopause. It is shown that the temperature response up to the mesopause is strongly influenced by changes in dynamics. During Northern Hemisphere summer, dynamical processes alone would lead to an almost global warming of up to 3 K in the uppermost mesosphere.
    Description: Published
    Description: 3903-3931
    Description: reserved
    Keywords: Sensitivity ; Chemistry ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
    Publication Date: 2021-05-19
    Description: The anthropogenic affectation was evaluated on the coast N of the Gulf of Batabanó in May 2003 (corresponding to the provinces of Matanzas and Havana), in areas located in the line of the coast. The results were compared with the historical information of the sector. In the coast N and the Ensenada of the Broa, the parameters oxygen saturation, DBO5 and DQO showed characteristic high values of eutrofication. The biggest contribution in the Cianoficies was in the near coastal areas to sources of organic contamination. In the case of the nutrients they show specific data of mesothrofic waters with tendency to the eutrofization and the silts presented a high affectation for toxic metals. The area near to Guanímar is distinguished to present conditions of organic contamination that favor heterothrofic conditions, corroborated by a prevalence of the processes of mineralization of the organic matter over primary production and lows values of fitoplankton concentration. On the contrary, in the region of Surgidero of Batabanó, the processes of synthesis of organic matter prevail suggested by a high primary production, and concentration of fitoplankton, with low breathing levels and mineralization of the organic matter, that indicates that the system is behaving autothrofically. In a general way, this sector is very affected by the anthropogenic impact. The information obtained is of great importance for the development of the fishing and tourist industries in the area.
    Description: Published
    Keywords: Phytoplankton ; Water quality ; Primary production ; Chemistry ; Environmental monitoring ; Phytoplankton ; Water quality ; Primary production ; Chemistry ; Environmental monitoring
    Repository Name: AquaDocs
    Type: Proceedings Paper
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  • 3
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    Alexandria: National Institute of Oceanography and Fisheries
    Publication Date: 2021-05-19
    Description: This journal is published by the NIOF, Egypt
    Description: Lake Manzalah; the largest delta Lake in Egypt represents a dynamic system that has been undergoing continuous and pronounced changes since long times. In the last year’s this Lake faced drastic problems that retarded its environmental and fisheries development; the most serious one is the discharge of waste water. It is attempted in the present study to investigate the chemical characters of Lake Manzalah water during 2001-2002. Water temperature ranged from an average of 12.35oC in January and 29.14oC in July. Dissolved Oxygen, pH and total dissolved solids were found in ranges optimum for the living of marine and freshwater fish species. The average concentrations of nutrients lied in the following ranges: 1.24 to 4.89 μmol PO4 -3 l-1 , 5.08 to 28.73 μmol SiO4 -2 l-1 and 1.81 to 17.7 μ_mol NO3-1 l-1 The concentrations of phosphorus and nitrogen compounds were found to be relatively higher at the southern regions of the Lake near to the outlets of the drains.
    Description: NIOF
    Description: Published
    Keywords: Hydrography ; Water ; Chemistry ; Chemical composition ; Water content ; Environment ; Chemical composition ; Environments ; Water content ; Fisheries
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 4
    Publication Date: 2022-05-25
    Description: Blooms of toxic or harmful microalgae, commonly called "red tides," represent a significant and expanding threat to human health and fisheries resources throughout the United States and the world. Ecological, aesthetic, and public health impacts include: mass mortalities of wild and farmed fish and shellfish, human intoxication and death from the consumption of contaminated shellfish or fish, alterations of marine food webs through adverse effects on larvae and other life history stages of commercial fish species, the noxious smell and appearance of algae accumulated in nearshore waters or deposited on beaches, and mass mortalities of marine mammals, seabirds, and other animals. In this report, we provide an estimate of the economic impacts of HABs in the United States from events where such impacts were measurable with a fair degree of confidence during the interval 1987-92. The total economic impact averaged $49 million per year, with public health impacts representing the largest component (45 percent). Commercial fisheries impacts were the next largest (37 percent of the total), while recreation/tourism accounted for 13 percent, and monitoring/management impacts 4 percent. These estimates are highly conservative, as many economic costs or impacts from HABs could not be estimated.
    Description: Funding was provided by the National Oceanic and Atmospheric Administration under Grants No. NA46RG0470 and NA90AA-D-SG480, the National Science Foundation under Grant No. OCE-9321244, and the Johnson Endowment of the Marine Policy Center.
    Keywords: Harmful algal blooms ; HABs ; Red tides ; Economic impacts ; Brown tides ; United States
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 5
    Publication Date: 2022-05-26
    Description: Thirteen short papers address aspects of competitiveness in the marine electronics instrumentation industry. Topics include activity and status of government initiatives in Japan and Europe to promote this industry; and the possible role of federal-state collaboration in the U.S. Papers address technology transfer between research institutions and the commercial sector; the role of "strategic alliances" in this process; and the "dual-use" concept in effective technology development and commercialization. Other papers address electronic technology applications in speific marine areas, such as the use and implications of the COMSAT mobile satellite communication infrastructure; electronic charts and safety of tanker operations; and instrumentation applications in aquaculture and environmental monitoring.
    Description: Funding was provided by the National Oceanic and Atmospheric Administration through a grant to the Massachusetts Centers of Excellence Corporation, grant No. NA87-AA-D-M00037.
    Keywords: Marine electronics ; Marine instruments ; Competitiveness ; Commercialization ; Marine economics ; State economic initiatives ; Technology transfer ; R&D ; Japan ; Europe ; United States ; Massachusetts ; Hawaii ; Aquaculture ; Tanker safety
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 6
    Publication Date: 2022-05-26
    Description: Originally issued as Reference No. 67-21
    Description: This supplement to Volume I of the Data File, Continental Margin, Atlantic Coast of the United States (Woods Hole Oceanographic Institution Ref. No. 66-8) consists of three parts: 1. Errata for Volume I, 2. New station and sample data added to the file, and 3. Miscellaneous tables of information pertaining to the file. The user is referred to Volume I for explanation of the headings and abbreviations used and for a discussion of the structure of the file.
    Description: Submitted to the U.S. Geological Survey under Contract No. 14-08-0001-8358.
    Keywords: Continental margins ; Oceanography ; United States
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 7
    Publication Date: 2023-01-19
    Description: Bromine monoxide (BrO) and sulphur dioxide (SO2) abundances as a function of the distance from the source were measured by ground-based scattered-light Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) in the volcanic plumes of Mt. Etna on Sicily, Italy in August-October 2004 and May 2005 and Villarica in Chile in November 2004. BrO and SO2 spatial distributions in a cross section of Mt. Etna’s plume were also determined by Imaging DOAS. We observed an increase in the BrO/SO2 ratio in the plume from below the detection limit near the vent to about 4.5 x 10-4 at 19 km (Mt. Etna) and to about 1.3 x 10-4 at 3 km (Villarica) distance, respectively. Additional attempts were undertaken to evaluate the compositions of individual vents on Mt. Etna. Furthermore, we detected the halogen species ClO and OClO. This is the first time that OClO could be detected in a volcanic plume. Using calculated thermodynamic equilibrium compositions as input data for a one–dimensional photochemical model, we could reproduce the observed BrO and SO2 vertical columns in the plume and their ratio as function of distance from the volcano as well as vertical BrO and SO2 profiles across the plume with current knowledge of multiphase halogen chemistry, but only when we assumed the existence of an ”effective source region”, where volcanic volatiles and ambient air are mixed at about 600°C (in the proportions of 60% and 40%, respectively)
    Description: Published
    Description: D06311
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Description: open
    Keywords: Chemistry ; Volcanic Plumes ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
    ISSN: 1476-5535
    Keywords: Penicillin V acylase ; Beijerinckia indica var.penicillanicum ; Mutation ; Solvent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Beijerinckia indica var.penicillanicum mutant UREMS-5, producing 168% more penicillin V acylase, was obtained by successive treatment with UV, γ-irradiation and ethylmethane sulfonate. Penicillin V acylase production by the mutant strain was resistant to catabolite repression by glucose. Incorporation of glucose, sodium glutamate and vegetable oils in the medium enhanced enzyme production. The maximum specific production of penicillin V acylase was 244 IU/g dry weight of cells. Effect of solvents on hydrolysis of penicillin V by soluble penicillin V acylase and whole cells was studied. Methylene chloride, chloroform and carbon tetrachloride significantly stimulated the rate of penicillin V hydrolysis by whole cells.
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  • 9
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    Journal of industrial microbiology and biotechnology 8 (1991), S. 99-106 
    ISSN: 1476-5535
    Keywords: Mutation ; UV ; Biodegradation ; Chlorinated organic compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In this study, a continuous-flow UV-induced mutation (CUM) device and the CUM device coupled to a selector (CUMS) reactor were fabricated and tested for their ability to enhance the probability of obtaining populations capable of chlorinated organic biodegradation. A mixed culture of bacteria were used as the starting strain for both the CUM and CUMS processes. Populations were obtained from the CUM and CUMS systems capable of 4-chlorobenzoic acid, 2,4-dichlorobenzoic acid and chlorendic acid biodegradation. Non-UV irradiated population served as controls for the experiments and did not demonstrate chlorinated organic biodegradation over the test duration.
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  • 10
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    Agriculture and human values 17 (2000), S. 279-283 
    ISSN: 1572-8366
    Keywords: Agri-food network ; Gender ; Sustainable agriculture ; United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Actor network theory and supply chainmanagement theory provide suggestive researchdirections for understanding regional agri-foodnetworks. These theories claim that relationshipsbased upon trust and cooperation are critical to thestrength and vitality of the network. This means thatexploring and detailing these relationships among thesuppliers, producers, workers, processors, brokers,wholesalers, and retailers within specific regionalgeographies of these networks are critical forfurthering cooperation and trust. Key areas ofcooperation include resource sharing andapprenticeship programs. Employing food networks as akey unit of contextual analysis will deepen ourunderstanding of how to enhance their resiliency andvibrancy. Important questions can be raised about thedifference gender makes for farmers, brokers,entrepreneurs, and workers in local food networks.
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  • 11
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    Current genetics 18 (1990), S. 441-445 
    ISSN: 1432-0983
    Keywords: Neurospora crassa ; Mutation ; RIP phenomenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the further analysis of a cross in which the mis-sense allele, am 3, of the Neurospora crassa am (glutamate dehydrogenase) gene was present in one parent together with two ectopic wild-type gene copies, one ascus was identified in which the two ectopic copies had been inactivated by the RIP process whereas the am 3 allele continued to produce its characteristic enzyme variety in active, but heat-sensitive, form. The am 3 allele had also acquired a new HindIII restriction site. It had no detectable methylation. The mutations responsible respectively for the new restriction site and the modified enzyme properties were separated from each other, and from the original am 3 mutation, by selecting for intragenic recombination on either side of the am 3 site. In this way two new effectively wild-type alleles were generated, one characterised by its heat-sensitive and kinetically modified enzyme product and the other by a new HindIII site. These results demonstrate that the RIP phenomenon can be a source of new functional alleles.
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  • 12
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    Journal of molecular evolution 35 (1992), S. 156-180 
    ISSN: 1432-1432
    Keywords: DNA damage ; DNA repair ; Chromatin ; Evolution ; Nucleosomes ; Nuclear matrix ; Active genes ; Z-DNA ; Sperm ; Mutation ; Molecular clock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Some evolutionary consequences of different rates and trends in DNA damage and repair are explained. Different types of DNA damaging agents cause nonrandom lesions along the DNA. The type of DNA sequence motifs to be preferentially attacked depends upon the chemical or physical nature of the assaulting agent and the DNA base composition. Higher-order chromatin structure, the nonrandom nucleosome positioning along the DNA, the absence of nucleosomes from the promoter regions of active genes, curved DNA, the presence of sequence-specific binding proteins, and the torsional strain on the DNA induced by an increased transcriptional activity all are expected to affect rates of damage of individual genes. Furthermore, potential Z-DNA, H-DNA, slippage, and cruciform structures in the regulatory region of some genes or in other genomic loci induced by torsional strain on the DNA are more prone to modification by genotoxic agents. A specific actively transcribed gene may be preferentially damaged over nontranscribed genes only in specific cell types that maintain this gene in active chromatin fractions because of (1) its decondensed chromatin structure, (2) torsional strain in its DNA, (3) absence of nucleosomes from its regulatory region, and (4) altered nucleosome structure in its coding sequence due to the presence of modified histones and HMG proteins. The situation in this regard of germ cell lineages is, of course, the only one to intervene in evolution. Most lesions in DNA such as those caused by UV or DNA alkylating agents tend to diminish the GC content of genomes. Thus, DNA sequences not bound by selective constraints, such as pseudogenes, will show an increase in their AT content during evolution as evidenced by experimental observations. On the other hand, transcriptionally active parts may be repaired at rates higher than inactive parts of the genome, and proliferating cells may display higher repair activities than quiescent cells. This might arise from a tight coupling of the repair process with both transcription and replication, all these processes taking place on the nuclear matrix. Repair activities differ greatly among species, and there is a good correlation between life span and repair among mammals. It is predicted that genes that are transcriptionally active in germ-cell lineages have a lower mutation rate than bulk DNA, a circumstance that is expected to be reflected in evolution. Exception to this rule might be genes containing potential Z-DNA, H-DNA, or cruciform structures in their coding or regulatory regions that appear to be refractory to repair. This study supports the molecular clock hypothesis when applied to one gene within a group of related species and contends that evolutionary rates might vary between genes and gene segments not only as a result of differences in selective constraints but also as a result of differences in the rate of damage minus rate of repair among different segments of chromatin DNA.
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  • 13
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    Journal of molecular evolution 39 (1994), S. 448-451 
    ISSN: 1432-1432
    Keywords: Synonymous substitution ; Escherichia coli ; Salmonella typhimurium ; Mutation ; Recombination ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial distribution of synonymous substitutions in enterobacterial genes is investigated. It is shown that synonymous substitutions are significantly clustered in such a way that a synonymous substitution in one codon elevates the rate of synonymous substitution in an adjacent codon by about 10%. The level of clustering does not appear to be related to the level of gene expression, and it is restricted to a range of two or three codons. There are at least three possible explanations: (1) sequence-directed mutagenesis, (2) recombination, and (3) selection.
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  • 14
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    Journal of paleolimnology 7 (1992), S. 191-214 
    ISSN: 1573-0417
    Keywords: geochemistry ; metals ; lake sediments ; paleolimnology ; United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by 210Pb and analyzed for water and organic content, eight major elements (Al, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO2, FeO, and to a lesser extent Ca and Al. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented distrubances in the watersheds; most disturbances are minor fires or selective logging. Accelerated accumulation of Pb from atmospheric sources into sediment first occurs in sediment dated between 1800 and 1850 in NY and NE, slightly later in the NGLS region, and about 1900 in FL. Modern accumulation rates in all areas are comparable (ca. 1 to 4 μg cm−2 yr−1). Accumulation rates of Pb in some lakes have declined significantly from 1975 to 1985. Atmospheric deposition of anthropogenic Zn and Cu is also indicated by generally increasing accumulation rates in sediment cores, but the record is not as clear nor are chemical profiles in all lakes parallel to the trends in atmospheric emissions inferred on the basis of fossil fuel consumption, smelting, and other industrial activities. Inter-lake variations in profiles of Cu and Zn are large. Vanadium accumulation rates increase by the 1940s in NY and NE, but not until the 1950s in the NGLS region. This timing correlates with regional trends in the combustion of fuel oil, a major source of atmospheric V. Acidification of some of the lakes is suggested by decreases in the concentration and accumulation rates of Mn, Ca, and Zn in recent sediment, relative to other elements of catchment origin. The decreases generally occur slightly before the onset of acidification as indicated by diatoms. Increased sediment accumulation rates for Fe may indicate the acidification of watershed soils. The use of the accumulation rate of TiO2 as an indicator of rates of erosion and for normalization of trace metal accumulation rates is in question for lakes where the flux of TiO2 from the atmosphere varies and is a significant fraction of the total flux of TiO2 to the sediment.
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  • 15
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    Mycopathologia 114 (1991), S. 117-126 
    ISSN: 1573-0832
    Keywords: dermatophytes ; survey ; United States ; humans ; 1985/87
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A survey of dermatophytes isolated from patients seeking medical advice was made from 1985 to 1987 in the United States. The survey included 54 locations with data from 45 cities and one state. Listing of the isolated dermatophytes and the frequency given by percentage of the total follows: Trichophyton rubrum 54.8%, T. tonsurans 31.3%, T. mentagrophytes 6.0%, Microsporum canis 4.0%, Epidermophyton floccosum 2.0%, M. gypseum 0.6%, and T. verrucosum 0.2%. Out of a total of 14,696 isolates M. audouinii was cultured 13 times, T. violaceum 12 times, M. nanum 6 times, T. terrestre 4 times, and T. soudanense twice. Single isolations were made of M.fulvum, M. ferrugineum and T. schoenleinii. Collection of dermatophyte data in Tucson, Arizona, began in 1966. In 1987, the first case of tinea capitis caused by T. tonsurans was observed. Other isolates of this organism as the cause of tinea capitis were made in this city during that year. These infections were in black children. With the recent growth of Tucson, the percentage of blacks in the population increased and this pathogen was introduced into the general population.
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  • 16
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    Pure and applied geophysics 134 (1990), S. 1-12 
    ISSN: 1420-9136
    Keywords: Precipitation ; trends ; climate changes ; data errors ; United States ; rainfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract There has been considerable interest in estimating secular trends in precipitation data in various regions of the world. It is therefore important to ascertain the manner in which errors of observation affect estimated trends. For this purpose we have compared trends at 1219 stations in the contiguous United States for two data sets: (a) original observations, also called “raw” observations, and (b) the observations, adjusted to compensate for suspected errors. The adjustments were made at the National Climate Data Center, Asheville (Quinlan et al., 1987;karl andWilliams, 1987), In order to focus on the effects of observational errors we attempted to avoid the effects of filling of missing data by limiting the analysis to the period 1940–1984 for which the number of missing values is much smaller than earlier periods. A least-square linear regression was performed on the raw and adjusted data for each station and the slopes of the fitted lines were compared. The comparison was made for monthly, seasonal and annual precipitation values. The results for annual precipitation showed that 23 percent of the stations have trends of opposite signs in the raw and adjusted data. The trends were identical in annual data at only 11 percent of the stations. When monthly data are combined to form seasonal and annual averages the magnitude of the difference between the slopes of the adjusted and the raw observations generally increases, indicating that the errors in the individual monthly observations are correlated. When the station data were averaged to obtain state-wide averages, the effects of the errors became less pronounced in most of the states. These results indicate that obtaining trends in precipitation from station data is a more difficult problem than has been realized.
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  • 17
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    Accreditation and quality assurance 5 (2000), S. 409-413 
    ISSN: 1432-0517
    Keywords: Key words Metrology ; Comparisons ; Chemistry ; Standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.
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  • 18
    ISSN: 1423-0127
    Keywords: AIDS ; Resistance ; Mutation ; Genotype ; Zidovudine ; Fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mutation L210W of HIV-1 reverse transcriptase (RT) is one of the six main mutations that confer in vivo resistance to zidovudine. Surprisingly, this mutation has received scant appraisal and its contribution to the genotypic resistance to nucleoside analogs is not well understood. The aim of this study was: (1) to study the frequency of mutation L210W in a large collection of HIV-1 sequences (2,049 samples, including 395 DNA and 1,654 RNA sequences) from patients receiving combination therapy, and (2) to analyze its association with the other mutations that confer resistance to zidovudine. A mutation at codon 210 (mainly L210W) was found in 647 (32%) of the 2,049 sequences analyzed. Only 43 (〈7%) of these 647 genomes were also mutated at codon 70 (p 〈 10−5). In contrast, 98% of these 647 sequences were also mutated at codon 215 (essentially T215Y/F), and 94% at codon 41 (mainly M41L). These data showing a close association between L210W, T215Y/F, and M41L, and a mutual exclusion between K70R and L210W, were confirmed by analyzing the sequences stored in the HIV-1 sequences available through the Stanford HIV RT and Protease Database. Follow-up studies demonstrated that L210W appeared always after T215Y/F. This observation is consistent with crystallographic studies which suggested that the aromatic side chain of Trp 210 could stabilize the interaction of Phe/Tyr215 with the dNTP-binding pocket. This molecular cross-talk between amino acid chains occurs nearby the conserved Asp113 residue. Since the lateral chain of Arg70 may also interact with Asp113, this is likely to create a sterical hindrance around this residue. Thus, the R→K reversion of codon 70 may represent a compensatory mechanism allowing a functional rearrangement of the dNTP-binding pocket in the mutated RT.
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  • 19
    ISSN: 1432-1211
    Keywords: Key words Amerindians ; Chileans ; HLA-A*6816 ; Mutation ; Gene conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 20
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    Plant cell reports 13 (1994), S. 372-376 
    ISSN: 1432-203X
    Keywords: Asparagus officinalis L ; Habituation ; Mutation ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Somatic embryogenesis from different genotypes of Asparagus officinalis L. could be obtained by in vitro culture of shoot apices. Apices were first cultured on an auxin-rich inducing medium and then transferred onto a hormone-free development medium. All genotypes tested in this way produced a few somatic embryos. In some experiments, during the development phase, a new kind of friable highly embryogenic tissue appeared in a random manner. These tissues could be continuously subcultured on a hormone-free medium and were named embryogenic lines. Five of these embryogenic lines regenerated plants from somatic embryos. These regenerated plants exhibited an increased embryogenic response compared to the parent plants; e.g. apex culture produced somatic embryos without any auxin treatments. For one of the embryogenic lines, a genetic analysis showed that the improved embryogenic response of regenerated plants was controlled by a mendelian dominant monogenic mutation.
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  • 21
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    Current genetics 26 (1994), S. 281-284 
    ISSN: 1432-0983
    Keywords: Ofloxacin ; Mitochondria ; Mutation ; Recombination ; Topoisomerase ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ofloxacin, a specific inhibitor of bacterial topoisomerase II, is known to inhibit the growth of yeast cells and to induce rho − mutants in the yeast S. cerevisiae. The frequency of ofloxacin-induced petite mutants under non-growth conditions was found to be strongly diminished when the cells were depleted in intramitochondrial ATP. Under optimal conditions of mitochondrial mutagenesis the drug induced mitotic recombination and reverse mutation in diploid strains but failed to cure either killer plasmids or the 2 μm DNA of dividing cells. The sensitivity to ofloxacin of the strains deficient in the DNA strandbreak repair pathway (rad52) was significantly higher then that of the wild-type strains and of the mutants deficient in excision or mutagenic DNA repair. The results are compatible with the idea that the cytotoxic and genetic activity of ofloxacin in yeast probably results from the inhibited DNA ligation function of topoisomerase II creating DNA breaks that are reparable through the recombination repair pathway.
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  • 22
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    Current genetics 23 (1993), S. 430-434 
    ISSN: 1432-0983
    Keywords: S. cerevisiae ; Mutational homozygosis ; Loss of heterozygosity ; Mutation ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A leucine-requiring hybrid of Saccharomyces cerevisiae, homoallelic at the LEU1 locus (leu1–12/leu1–12) and heterozygous for three chromosome-VII genetic markers distal to the LEU1 locus, was employed to inquire: (1) whether spontaneous gene mutation and mitotic segregation of heterozygous markers occur in positive nonrandom association and (2) whether homozygous LEU1/LEU1 mutant diploids are generated. The results demonstrate that gene mutation of leu1–12 to LEU1 and mitotic segregation of heterozygous chromosome-VII markers occur in strong positive nonrandom association, suggesting that the stimulatory DNA lesion is both mutagenic and recombinogenic. In addition, genetic analysis of diploid Leu+ revertants revealed that approximately 3% of mutations of leu1–12 to LEU1 result in LEU1/LEU1 homozygotes. Red-white sectored Leu+ colonies exhibit genotypes that implicate postreplicational chromatid breakage and exchange near the site of leu1–12 reversion, chromosome loss, and subsequent restitution of diploidy, in the sequence of events leading to mutational homozygosis. By analogy, diploid cell populations can yield variants homozygous for novel recessive gene mutations at biologically significant rates. Mutational homozygosis may be relevant to both carcinogenesis and the evolution of asexual diploid organisms.
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  • 23
    ISSN: 1432-072X
    Keywords: Fatty acids ; Mortierella alpina ; ω3-Desaturation ; Mutation
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    Notes: Abstract A mutant considered to be defective in the conversion of n-6 to n-3 fatty acids (ω3-desaturation) was derived from a Δ5-desaturation-defective mutant (Mut44) of Mortierella alpina 1S-4, after treating its spores with N-methyl-N′-nitro-N-nitrosoguanidine. This mutant cannot produce 8(Z),11(Z),14(Z),17(Z)-eicosatetraenoic acid or any other n-3 fatty acids, of which about 10% was found in its parental strain upon cultivation at 12°C. The mutant's growth rate was comparable to that of the parental strain when grown at 28°C, but it became much slower when the mutant grew at 12°C, at which the lag phase for Mut44 was about 2 d but 5 d for the mutant.
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  • 24
    ISSN: 1432-072X
    Keywords: Temperature ; Mutation ; Thermotolerance ; Escherichia coli ; Salmonella typhimurium ; Pseudomonas aeruginosoa ; DNA gyrase ; gyrA ; Nalidixic acid
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    Topics: Biology
    Notes: Abstract A prolonged incubation of Escherichia, Salmonella or Pseudomonas at 48°C with nalidixic acid selected mutants (T48) able to grow at 48°C. A prolonged incubation at 54°C of the T48 mutants selected mutants (T54) able to grow at 54°C. These mutants were susceptible to the same bacteriophages as the original mesophilic strains. Auxotrophic phenotypes of Escherichia coli and Salmonella typhimurium mesophilic parents were demonstrated by these mutants if they were cultivated on minimal agar with cellobiose at 48°C or 54°C or on a minimal agar with glucose at 37°C. The T48 alleles mapped in the gyrA region of E. coli or S. typhimurium chromosome. In S. typhimurium the T54 alleles, which permit growth at 54°C, were shown by cotransductional analysis to be linked to gyrA.
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  • 25
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    Archives of microbiology 159 (1993), S. 98-100 
    ISSN: 1432-072X
    Keywords: Prophage induction ; Weigle reactivation ; Mutation ; Filamentation ; Nitrofurantoin ; Vibrio cholerae el tor
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    Topics: Biology
    Notes: Abstract Treatment of Vibrio cholerae el tor strain SLH22(J) with nitrofurantoin induced dose-dependent prophage ‘kappa’, the maximum induction being 6-fold the spontaneous induction level. UV-inactivated ‘kappa’ phages were Weigle reactivated, the maximum Weigle factor being 1.8 and 2.0 respectively in nitrofurantoin and UV pretreated el tor strain H218 Smr. Nitrofurantoin treatment also caused significant filamentation of the el tor strain H218 Smr and mutation of these cells from ampicillin sensitivity to ampicillin resistance. The levels of the four SOS-like responses induced by this drug were low but significant.
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  • 26
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    Astrophysics and space science 216 (1994), S. 153-154 
    ISSN: 1572-946X
    Keywords: Chemistry ; Molecular Hydrogen ; Cloud Models
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    Topics: Physics
    Notes: Abstract Observations of the CO J=1-0 line are commonly used as a tracer for molecular material in clouds. The ratio of the H2 column density to the integrated intensity of this line,X, is often taken to be constant, despite theoretical and observational uncertainty. We have tried to identify how this ratio depends on cloud parameters, testing a simple theoretical argument suggesting its invariance with respect to density. The apparent constancy can be understood if clouds are clumpy on scales of Av ≈ 1-2 mag.
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  • 27
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    Journal of mathematical biology 33 (1994), S. 111-137 
    ISSN: 1432-1416
    Keywords: B-cells ; Immune system ; Idiotypic networks ; Mutation ; Replicator equations
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    Topics: Biology , Mathematics
    Notes: Abstract In order to evaluate the role of idiotypic networks in the operation of the immune system a number of mathematical models have been formulated. Here we examine a class of B-cell models in which cell proliferation is governed by a non-negative, unimodal, symmetric response function f(h), where the field h summarizes the effect of the network on a single clone. We show that by transforming into relative concentrations, the B-cell network equations can be brought into a form that closely resembles the replicator equation. We then show that when the total number of clones in a network is conserved, the dynamics of the network can be represented by the dynamics of a replicator equation. The number of equilibria and their stability are then characterized using methods developed for the study of second-order replicator equations. Analogies with standard Lotka-Volterra equations are also indicated. A particularly interesting result of our analysis is the fact that even though the immune network equations are not second-order, the number and stability of their equilibria can be obtained by a superposition of second-order replicator systems. As a consequence, the problem of finding all of the equilibrium points of the nonlinear network equations can be reduced to solving linear equations.
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    Journal of mathematical biology 30 (1992), S. 597-632 
    ISSN: 1432-1416
    Keywords: Autocatalysis ; Mutation ; Perturbation theory ; Qualitative analysis ; Replication dynamics
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    Topics: Biology , Mathematics
    Notes: Abstract A class of kinetic equations describing catalysed and template induced replication, and mutation is introduced. This ODE in its most general form is split into two vector fields, a replication and a mutation field. The mutation field is considered as a perturbation of the replicator equation. The perturbation expansion is a Taylor series in a mutation parameter λ. First, second and higher order contributions are computed by means of the conventional Rayleigh-Schrödinger approach. Qualitative shifts in the positions of rest points and limit cycles on the boundary of the physically meaningful part of concentration space are predicted from flow topologies. The results of the topological analysis are summarized in two theorems which turned out to be useful in applications: the rest point migration theorem (RPM) and the limit cycle migration theorem (LCM). Quantitative expressions for the shifts of rest points are computed directly from the perturbation expansion. The concept is applied to a collection of selected examples from biophysical chemistry and biology.
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  • 29
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    The journal of membrane biology 139 (1994), S. 203-212 
    ISSN: 1432-1424
    Keywords: Mg2+ current ; Mutation ; Paramecium ; Intracellular Mg2+ homeostasis
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract “Eccentric” is a newly-isolated mutant of Paramecium tetraurelia that fails to swim backwards in response to Mg2+. In the wild type, this backward swimming results from Mg2+ influx via a Mg2+-specific ion conductance (I Mg. Voltage-clamp analysis confirmed that, as suspected, step changes in membrane potential over a physiological range fail to elicit I Mg from eccentric. Further electrophysiological investigation revealed a number of additional ion-current defects in eccentric: (i) The Ca2+ current activated upon depolarization inactivates more slowly in eccentric than in the wild type, and it requires longer to recover from this inactivation. (ii) The Ca2+-dependent Na+ current deactivates significantly faster in the mutant, (iii) The two K+ currents observed upon hyperpolarization are reduced by 〉60% in eccentric. It is difficult to envision how these varied pleiotropic effects could result from loss of a single ion current. Rather, they suggest that the eccentric mutation affects a global regulatory system. Two plausible hypotheses are discussed.
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  • 30
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    Journal of mathematical biology 30 (1992), S. 597-631 
    ISSN: 1432-1416
    Keywords: Autocatalysis ; Mutation ; Perturbation theory ; Qualitative analysis ; Replication dynamics
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    Topics: Biology , Mathematics
    Notes: Abstract A class of kinetic equations describing catalysed and template induced replication, and mutation is introduced. This ODE in its most general form is split into two vector fields, a replication and a mutation field. The mutation field is considered as a perturbation of the replicator equation. The perturbation expansion is a Taylor series in a mutation parameter λ. First, second and higher order contributions are computed by means of the conventional Rayleigh-Schrödinger approach. Qualitative shifts in the positions of rest points and limit cycles on the boundary of the physically meaningful part of concentration space are predicted from flow topologies. The results of the topological analysis are summarized in two theorems which turned out to be useful in applications: the rest point migration theorem (RPM) and the limit cycle migration theorem (LCM). Quantitative expressions for the shifts of rest points are computed directly from the perturbation expansion. The concept is applied to a collection of selected examples from biophysical chemistry and biology.
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    Journal of mathematical biology 31 (1993), S. 123-132 
    ISSN: 1432-1416
    Keywords: Genealogy ; Coalescent ; Mutation ; Migration ; Markov chain
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    Topics: Biology , Mathematics
    Notes: Abstract The genealogical process of neutral genes with mutation in geographically structured populations is investigated. Following Watterson [24], the sampled genes are partitioned into two types, old equivalence classes and new equivalence classes. The model is described by a bivariate continuous time Markov chain as an interactive particle system. Some results are obtained in the two-population model and the stepping stone model with symmetric nearest-neighbour migration.
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    Journal of mathematical biology 32 (1993), S. 33-44 
    ISSN: 1432-1416
    Keywords: Mutation ; Selection ; Random drift ; Muller's ratchet
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    Notes: Abstract Two independently derived theories predict upper limits to the mutation rate beyond which evolution cannot be controlled by natural selection. One is the theory of Muller's ratchet, explaining the low phylogenetic age of parthenogenetic clones, the other one is the theory of error thresholds, predicting the maximal information content of selfreplicating molecules in prebiotic evolution. Both theories are based on similiar mathematical models but reach qualitatively different conclusions. Muller's ratchet only works in finite populations, while error thresholds are a deterministic phenomenon. In this paper it is shown that this discrepancy is due to different assumptions about the fitness values the selfreplicative units are allowed to assume. If no lower limit for the fitness values is assumed then the deterministic equilibrium frequency of the currently best genotype is strictly positive, no matter how strong mutation is, and random drift is required to cause its extinction (Muller's ratchet). On the other hand, positive lower limits for the fitness values lead to zero equilibrium frequencies in the deterministic description provided the mutation rate is high enough and no back mutations occur.
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  • 33
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    Journal of mathematical biology 32 (1994), S. 193-218 
    ISSN: 1432-1416
    Keywords: Selection ; Mutation ; Mutation load ; Quantitative genetic traits
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    Topics: Biology , Mathematics
    Notes: Abstract Haldane (1937) showed that the reduction of equilibrium mean fitness in an infinite population due to recurrent deleterious mutations depends only on the mutation rate but not on the harmfulness of mutants. His analysis, as well as more recent ones (cf. Crow 1970), ignored back mutation. The purpose of the present paper is to extend these results to arbitrary mutation patterns among alleles and to quantitative genetic traits. We derive first-order approximations for the equilibrium mean fitness (and the mutation load) and determine the order of the error term. For a metric trait under mutation-stabilizing-selection balance our result differs qualitatively from that of Crow and Kimura (1964), whose analysis is based on a Gaussian assumption. Our general approach also yields a mathematical proof that the variance under the usual mutation-stabilizing-selection model is, to first order, µ/s (the house-of-cards approximation) as µ/s tends to zero. This holds for arbitrary mutant distributions and does not require that the population mean coincide with the optimum. We show how the mutant distribution determines the order of the error term, and thus the accuracy of the house-of-cards approximation. Upper and lower bounds to the equilibrium variance are derived that deviate only to second order as µ/s tends to zero. The multilocus case is treated under the assumption of global linkage equilibrium.
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  • 34
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    Journal of mathematical biology 30 (1991), S. 199-213 
    ISSN: 1432-1416
    Keywords: Polygenic dynamics ; Quantitative trait ; Selection ; Mutation ; Cumulants ; Generating function
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    Notes: Abstract A new approach for describing the evolution of polygenic traits subject to selection and mutation is presented. Differential equations for the change of cumulants of the allelic frequency distribution at a particular locus and for the cumulants of the distributions of genotypic and phenotypic values are derived. The derivation is based on the assumptions of random mating, no sex differences, absence of random drift, additive gene action, linkage equilibrium, and Hardy-Weinberg proportions. Cumulants are a set of parameters that, like moments, describe the shape of a probability density. Compared with moments, however, they have properties that make them a much more convenient tool for investigating polygenic traits. Applications to directional and stabilizing selection are given.
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  • 35
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    Theoretical and applied genetics 87 (1994), S. 657-667 
    ISSN: 1432-2242
    Keywords: Transposable elements ; Mutation ; Evolution ; DNA repair ; Gene conversion
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    Topics: Biology
    Notes: Abstract The mobile DNAs of the Mutator system of maize (Zea mays) are exceptional both in structure and diversity. So far, six subfamilies of Mu elements have been discovered; all Mu elements share highly conserved terminal inverted repeats (TIRs), but each sub-family is defined by internal sequences that are apparently unrelated to the internal sequences of any other Mu subfamily. The Mu1/Mu2 subfamily of elements was created by the acquisition of a portion of a standard maize gene (termed MRS-A) within two Mu TIRs. Beside the unusually long (185–359 bp) and diverse TIRs found on all of these elements, other direct and inverted repeats are often found either within the central portion of a Mu element or within a TIR. Our computer analyses have shown that sequence duplications (mostly short direct repeats interrupted by a few base pairs) are common in non-autonomous members of the Mutator, Ac/Ds, and Spm(En) systems. These duplications are often tightly associated with the element-internal end of the TIRs. Comparisons of Mu element sequences have indicated that they share more terminal components than previously reported; all subfamilies have at least the most terminal 215 bp, at one end or the other, of the 359-bp Mu5 TIR. These data suggest that many Mu element subfamilies were generated from a parental element that had termini like those of Mu5. With the Mu5 TIRs as a standard, it was possible to determine that elements like Mu4 could have had their unusual TIRs created through a three-step process involving (1) addition of sequences to interrupt one TIR, (2) formation of a stem-loop structure by one strand of the element, and (3) a subsequent DNA repair/gene conversion event that duplicated the insertion(s) within the other TIR. A similar repair/conversion extending from a TIR stem into loop DNA could explain the additional inverted repeat sequences added to the internal ends of the Mu4 and Mu7 TIRs. This same basic mechanism was found to be capable of generating new Mu element subfamilies. After endonucleolytic attack of the loop within the stem-loop structure, repair/conversion of the gap could occur as an intermolecular event to generate novel internal sequences and, therefore, a new Mu element subfamily. Evidence supporting and expanding this model of new Mu element subfamily creation was identified in the sequence of MRS-A.
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    Russian journal of marine biology 26 (2000), S. 432-438 
    ISSN: 1608-3377
    Keywords: Mutation ; phylogeny ; nuclear DNA ; mitochondrial DNA ; salmonid fishes ; divergence time
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    Topics: Biology
    Notes: Abstract Mutation rates of the mitochondrial and nuclear genomes of salmonid fishes were assessed on the basis of a phylogenetic study of 12 species representing four genera of the family Salmonidae. Analysis of the extent of divergence of the masu salmon Oncorhynchus masou and the Pacific trout Parasalmo suggests a high rate of mtDNA mutation in the masu salmon. However, the nuclear genome in this species has mutated relatively slowly. For the other 5 species of Pacific salmon, no discrepancy was found in the mutation rates of mitochondrial and nuclear DNA. Values of the absolute time of divergence of taxa, calculated for the two independently inherited parts of the salmonid genome, were approximately within the same range and coincided with those based on evolutionary hypotheses [1, 21].
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  • 37
    ISSN: 1617-4623
    Keywords: Key wordsDrosophila ; Cytogenetic region 44D-45B ; EMS mutagenesis ; Mutation
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    Topics: Biology
    Notes: Abstract We have performed an F2 genetic screen to identify lethal mutations that map to the 44D-45B region of the Drosophila melanogaster genome. By screening 8500 mutagenized chromosomes for lethality over Df(2R)Np3, a deficiency which encompasses nearly 1% of the D. melanogaster euchromatic genome, we recovered 125 lines with lethal mutations that represent 38 complementation groups. The lethal mutations have been mapped to deficiencies that span the 44D-45B region, producing an approximate map position for each complementation group. Lethal mutations were analyzed to determine the phase of development at which lethality occurred. In addition, we have linked some of the complementation groups to P element-induced lethals that map to 44D-45B, thus possibly providing new alleles of a previously tagged gene. Some of the complementation groups represent potentially novel alleles of previously identified genes that map to the region. Several genes have been mapped by molecular means to the 44D-45B region, but do not have any reported mutant alleles. This screen may have uncovered mutant alleles of these genes. The results of complementation tests with previously identified genes in 44D-45B suggests that over half of the complementation groups identified in this screen may be novel.
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  • 38
    ISSN: 1617-4623
    Keywords: Rice ; Tetraploid irradiation ; Genome rearrangement ; rDNA ; Mutation
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    Topics: Biology
    Notes: Abstract The organization of tandemly repeated sequences of ribosomal DNA (rDNA) in rice mutants derived from γ-irradiated tetraploids was analyzed. Southern hybridization analysis of nuclear DNA revealed that most of the intergenic spacers (IGSs) in mutant rDNA are replaced concertedly by new molecular species. The new IGSs are produced by the amplification of a subrepeat of about 250 bp. Results obtained from sequence analyses indicate that various intermediate molecular species of the subrepeat were formed during structuring of the IGS region and that many rearrangements occurred between them. These findings demonstrate the effectiveness of recurrent irradiation of tetraploids for inducing artificial genome rearrangement, and also indicate the extreme plasticity and variability of genome structure in plants.
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  • 39
    ISSN: 1617-4623
    Keywords: TOL plasmid ; Biodegradation ; Pseudornonas putida ; Evolution ; Mutation
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    Topics: Biology
    Notes: Abstract TOL plasmid pWW0 from Pseudomonas putida mt-2 encodes catabolic enzymes required for the oxidation of toluene and xylenes. The structural genes for these catabolic enzymes are clustered into two operons, the xylCMABN operon, which encodes a set of enzymes required for the transformation of toluene/xylenes to benzoate/toluates, and the xylXYZLTEGFJQKIH operon, which encodes a set of enzymes required for the transformation of benzoate/toluates to Krebs cycle intermediates. The latter operon can be divided physically and functionally into two parts, the xylXYZL cluster, which is involved in the transformation of benzoate/toluates to (methyl)catechols, and the xylTEGFJQKIH cluster, which is involved in the transformation of (methyl)catechols to Krebs cycle intermediates. Genes isofunctional to xylXYZL are present in Acinetobacter calcoaceticus, and constitute a benzoate-degradative pathway, while xylTEGFJQKIH homologous encoding enzymes of a methylphenol-degradative pathway and a naphthalene-degradative pathway are present on plasmid pVI150 from P. putida CF600, and on plasmid NAH7 from P. putida PpG7, respectively. Comparison of the nucleotide sequences of the xylXYZLTEGFJQKIH genes with other isofunctional genes suggested that the xylTEGFJQKIH genes on the TOL plasmid diverged from these homologues 20 to 50 million years ago, while the xylXYZL genes diverged from the A. calcoaceticus homologues 100 to 200 million years ago. In codons where amino acids are not conserved, the substitution rate in the third base was higher than that in synonymous codons. This result was interpreted as indicating that both single and multiple nucleotide substitutions contributed to the amino acid-substituting mutations, and hence to enzyme evolution. This observation seems to be general because mammalian globin genes exhibit the same tendency.
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    Biodiversity and conservation 9 (2000), S. 1313-1322 
    ISSN: 1572-9710
    Keywords: BIOCLIM ; birds ; conservation strategies ; ecological niche modeling ; endangered species ; GARP ; United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A first exploration of applications of ecological niche modeling and geographic distributional prediction to endangered species protection is developed. Foci of richness of endangered bird species are identified in coastal California and along the southern fringe of the United States. Species included on the Endangered Species List on the basis of peripheral populations inflate these concentrations considerably. Species without protection in the US National Park System are focused particularly in peninsular Florida. Application of this methodology to additional taxa and regions holds promise for diverse conservation applications.
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    Pharmacy world & science 16 (1994), S. 55-61 
    ISSN: 1573-739X
    Keywords: AMP deaminase/deliciency ; Deficiency diseases ; Genetics, biochemical ; Mutation
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    Topics: Chemistry and Pharmacology
    Notes: Abstract In man, there are at least four isoforms of adenosine monophosphate deaminase (AMPD): myoadenylate deaminase in skeletal muscle, the L isoform in liver, and the E1 and E2 isoforms in erythrocytes. Myoadenylafe deaminase is encoded by the AMPD1 gene located on chromosome 1 p13-p21, the L isoform by the AMPD2 gene, and both isoforms in erythrocytes by the AMPD3 gene. Myoadenylate deaminase deficiency is found in 2–3% of all muscle biopsies. The inborn type of myoadenylate deaminase deficiency is caused by a single mutant allele harbouring two mutations: C34→T (Gin→Stop) and C143→T (Pro-48→Leu). Population studies revealed a frequency of the mutant allele of 0.12 in Caucasian Americans and Germans. The C34→T mutation is located in exon 2, which is alternatively spliced in part of the AMPD1 transcript in human muscle. Since the second mutation does not affect enzyme function, alternatively spliced mRNA encodes a catalytically active enzyme. Only one patient with a disorder linked to liver AMPD has been described so far. In this patient the decreased inhibition of this enzyme by GTP resulted in uric acid overproduction and gout. A complete lack of erythrocyte AMPD activity is found in asymptomatic subjects. The molecular basis of both disorders is not yet known.
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  • 42
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
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    Pharmacy world & science 13 (1991), S. 109-118 
    ISSN: 1573-739X
    Keywords: Chemistry ; Consumer product safety ; Drug packaging ; Environmental pollution ; Plasticizers ; Polyvinyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this report the state of the art with respect to PVC as pharmaceutical packaging material is described. A general introduction into the applications of PVC is followed by a description of its production process. The metabolic effects of the monomer of PVC, vinyl chloride and of the most commonly used plasticizer diethylhexylphthalate are mentioned. Special attention is given to the pharmaceutical properties of plasticized PVC bags in comparison to other plastics and the environmental aspects of waste PVC disposal. Although there are emotional and political queries regarding the future use of PVC as a (pharmaceutical) packaging material, we conclude that there is no scientific justification for a total or partial ban of PVC. PVC will remain a fact of life as a cheap, versatile, high-performance and well-investigated plastic material for medical and pharmaceutical applications, to be replaced by newer plastics only for certain well-defined indications where the requirements of the plastic to be used are so specific that it will economically and technically be justified to use another polymer. Community and hospital pharmacists have to be prepared for a role in intake of waste plastic disposables, probably against deposit money, in order to fulfil the logistics needed for recycling.
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    Natural resources research 1 (1992), S. 153-162 
    ISSN: 1573-8981
    Keywords: Oil and gas assessment ; Analytic probability ; Play analysis ; United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A geostochastic system called FASPF was developed by the U.S. Geological Survey for their 1989 assessment of undiscovered petroleum resources in the United States. FASPF is a fast appraisal system for petroleum play analysis using a field-size geological model and an analytic probabilistic methodology. The geological model is a particular type of probability model whereby the volumes of oil and gas accumulations are modeled as statistical distributions in the form of probability histograms, and the risk structure is bilevel (play and accumulation) in terms of conditional probability. The probabilistic methodology is an analytic method derived from probability theory rather than Monte Carlo simulation. The resource estimates of crude oil and natural gas are calculated and expressed in terms of probability distributions. The probabilistic methodology developed by the author is explained. The analytic system resulted in a probabilistic methodology for play analysis, subplay analysis, economic analysis, and aggregation analysis. Subplay analysis included the estimation of petroleum resources on non-Federal offshore areas. Economic analysis involved the truncation of the field size with a minimum economic cutoff value. Aggregation analysis was needed to aggregate individual play and subplay estimates of oil and gas, respectively, at the provincial, regional, and national levels.
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    Plant systematics and evolution 171 (1990), S. 1-14 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Compositae ; Chemistry ; systematics ; evolution
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    Topics: Biology
    Notes: Abstract The broad knowledge of the chemistry of theCompositae allows the discussion of its relevance for the systematics and evolution within the family. Furthermore a separation into subfamilies can be supported by the observed differences in the distribution of the main constituents in the tribes.
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  • 46
    ISSN: 1617-4623
    Keywords: Retroposon ; Transposable element ; Mutation
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    Topics: Biology
    Notes: Summary We analysed the structure of the white locus of Drosophila melanogaster in a family of related white mutants. The white-one mutant has bleach white eyes, and a Doc transposable element is inserted into the promoter region of the white locus. The DNA sequence of this Doc insertion was determined, and showed it to be closely related to other Drosophila melanogaster retroposons such as the I factor and the F, G and jockey elements. There are two long open reading frames, which encode a putative nucleic acid binding protein and a putative reverse transcriptase, respectively. Two independent, partially pigmented derivatives were analysed by cloning sequences from this region. In white-honey a transposable element of the retroviral class, B104, is inserted within the Doe element. In white-eosin there is an insertion within the Doc element of a 190 by sequence that appears to be a member of a novel family of transposable elements. This pogo element is of the same structural class as the Drosophila melanogaster P and hobo elements. These data are consistent with the hypothesis that the Doc retroposon cannot excise, and that, for the white-one mutation, flies with altered phenotypes are most often generated by the insertion of additional transposable elements.
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    Molecular genetics and genomics 244 (1994), S. 295-302 
    ISSN: 1617-4623
    Keywords: DNA repair ; Recombination ; Virulence ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recA + gene of Vibrio cholerae O1 has been cloned, its nucleotide sequence determined and the product characterized. A deletion mutation was constructed in the recA gene and mutants showed the typical sensitivity to UV and to DNA-damaging agents, as well as an inability to mediate homologous DNA recombination. The chromosomal recA deletion mutants in V. cholerae do not show altered virulence in the infant mouse cholera model and are thus ideal strains for use in complementation studies.
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  • 48
    ISSN: 1617-4623
    Keywords: Streptococcus pyogenes ; vir regulon ; emm-related genes ; Recombination ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One of the most prevalent genetic lineages of group A streptococci (GAS) harbors a genomic locus termed the large vir regulon, which contains an emm gene encoding the antiphagocytic M protein, and structurally related fcrA and enn (emm-related) genes encoding immunoglobulin-binding proteins. In the present study more than 100 large vir regulons from 42 different GAS serotypes were analyzed by PCR and partial DNA sequencing. On comparing these data to published sequences, sites of mutational and putative recombinational events were identified and ordered with respect to their intra/intergenic or intra/intergenomic nature. The emm-related genes were found to display small intragenic deletions or insertions, were completely deleted from, or newly inserted into the genome, or were fused to adjacent genes. Intergenomic exchanges of complete emm-related genes, or segments thereof, between different vir regulons were detected. Most of these processes seem to involve short flanking direct repeats. Occasionally, the structural changes could be correlated with changes in the functions of the encoded proteins.
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  • 49
    ISSN: 1617-4623
    Keywords: Deficiency mapping ; Mutation ; Telomere Chromosome structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutator, mu2, in Drosophila melanogaster has been identified recently that potentiates the recovery of terminal deficiencies. The deleted chromosomes behave as if they had been capped; that is, they are protected from degradation and from fusion with other chromosome fragments. The mutator maps near the telomere on the left arm of chromosome 3. Using the selectable marker Aprt, 150 deficiencies for region 62 of the cytological map have been recovered. These deficiencies identify the map position of mu2 as 62B11-C1. A yeast artificial chromosome spanning this region has been subcloned into lambda phage, and the positions of deficiency breakpoints on either side of the mu2 gene have been identified within the subclones. These positions limit the location of the left end of the gene to a 23 kb region. In the course of these experiments, three additional, presumptive mutant alleles were identified, suggesting that other mutator alleles remain undiscovered in many standard laboratory stocks.
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  • 50
    ISSN: 1617-4623
    Keywords: Hordeum vulgare L. ; Nitrite reduction ; Mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eleven green individuals were isolated when 95000 M2 plants of barley (Hordeum vulgare L.), mutagenised with azide in the M1, were screened for nitrite accumulation in their leaves after nitrate treatment in the light. The selected plants were maintained in aerated liquid culture solution containing glutamine as sole nitrogen source. Not all plants survived to flowering and some others that did were not fertile. One of the selected plants, STA3999, from the cultivar Tweed could be crossed to the wild-type cultivar and analysis of the F2 progeny showed that leaf nitrite accumulation was due to a recessive mutation in a single nuclear gene, which has been designated Nir1. The homozygous nir1 mutant could be maintained to flowering in liquid culture with either glutamine or ammonium as sole nitrogen source, but died within 14 days after transfer to compost. The nitrite reductase cross-reacting material seen in nitrate-treated wild-type plants could not be detected in either the leaf or the root of the homozygous nir1 mutant. Nitrite reductase activity, measured with dithionite-reduced methyl viologen as electron donor, of the nitrate-treated homozygous nir1 mutant was much reduced but NADH-nitrate reductase activity was elevated compared to wild-type plants. We conclude that the Nir1 locus determines the formation of nitrite reductase apoprotein in both the leaf and root of barley and speculate that it represents either the nitrite reductase apoprotein gene locus or, less likely, a regulatory locus whose product is required for the synthesis of nitrite reductase, but not nitrate reductase. Elevation of NADH-nitrate reductase activity in the nir1 mutant suggests a regulatory perturbation in the expression of the Narl gene.
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    Environmental and resource economics 1 (1991), S. 385-413 
    ISSN: 1573-1502
    Keywords: Environmental standards ; environmental regulations ; benefit-cost ; cost-benefit ; United States ; efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract This paper summarizes the results of the first systematic, geographically-specific efficiency assessment of the U.S. experience with national environmental standards and with alternative approaches to establishing those standards. This ex-post evaluation assessed the net benefits that resulted from EPA's regulation of conventional air and water pollutants from the pulp and paper industry between 1973 and 1984. The paper compares the benefit-cost efficiencies of the three dominant regulatory approaches: technology, ambient, and benefits. Unlike previous studies, which assessed benefits and costs on a national basis, the study estimates both costs and benefits on a facility-by-facility basis. The analysis shows how the efficiency of national environmental regulations can vary dramatically at local levels. The authors conclude that the technology-based standards for water pollution management failed as an efficient environmental strategy. The costs clearly exceeded the benefits in the aggregate, as well as in the specific in most situations. Benefits exceeded costs at only 11 of the 68 mills investigated. The ambient based standards for air pollution management succeeded as an environmental strategy in the aggregate, but succeeded in the specific for only one-third of the mills (22 of 60 mills). The benefits-based standards for air pollution management also succeeded in the aggregate as well as in the specific for about one-half of the mills. Benefits exceeded costs at 29 of the 60 mills investigated. The results of the study point to two major conclusions. First, a regulatory policy that is based on some measure of environmental results, either ambient-based or benefits-based, will be more efficient than a policy that ignores environmental results. Second, truly efficient policies for reducing environmental risks require pollution mitigation decisions that take into account local conditions. These include not only the changes in local ambient conditions, but also the number of people who will benefit from pollution reduction decisions. This latter conclusion suggests that national environmental standards per se may be inefficient.
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    Earth, moon and planets 88 (2000), S. 35-58 
    ISSN: 1573-0794
    Keywords: Chemistry ; interplanetary dust particles (IDPs) ; Leonids ; meteor trails ; meteoroids ; meteors ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection''ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission.
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    GeoJournal 50 (2000), S. 105-108 
    ISSN: 1572-9893
    Keywords: community ; Czech Republic ; East Central Europe ; ethnicity ; migration ; Prague ; social exclusion ; transnationalism ; United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract Migration flows from western Europe, the United States and Canada to east central Europe have received little attention so far. But numbers are now considerable and in the context of globalisation it seems appropriate to conceptualise communities of Westerners in terms of transnational social spaces as defined by Glick Schiller et al. Study of Americans in Prague reveals three main groups: enterprise managers, lifestyle migrants and entrepreneurs in small and medium-sized enterprises. All are engaged in a variety of different processes of community-building, often with clear trends towards a new transnationalism. Yet, the individual attempt to live in two societies is limited by the marked boundaries of the communities and by the degree of social exclusion which they experience from the majority population.
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  • 54
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    Angewandte Makromolekulare Chemie 175 (1990), S. 107-116 
    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: Zur Beschreibung der Polymerisationsgeschwindigkeit der radikalischen Fallungspolymerisation von Acrylsäure in Toluol wurde ein Modell entewickelt. Die experimentelle Überprüfung des Modells erfolgte durch Messungen in einem isotherm betriebenen Reaktionskalorimeter. Das Modell beschreibt die Polymerisationsgeschwindigkeit bis zum vollständigen Umsatz in einem Temperaturbereich von 40 bis 60°C.
    Notes: A kinetic model for the free-radical precipitation polymerization of acrylic acid in toluene was developed and verified experimentally by using an isothermal reaction calorimeter. The model predicts the rate of polymerization accurately up to complete conversion in the temperature range of 40 to 60°C.
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    Angewandte Makromolekulare Chemie 175 (1990), 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: Es wird über Untersuchungen an Legierungen aus isotaktischem Polypropylen und EPDM-Elastomer berichtet, die mit hochenergetischen Elektronen bestrahlt worden waren. Die Mischungsverhältnisse in den Proben überstrichen sowohl den für elastomermodifizierte Thermoplaste typischen Bereich als auch den der thermoplasticschen Elastomeren. Eine Vernetzung der Komponenten über die Grenzfläche hinweg wurde nachgewiesen. Diese grenzflächenübergreifende Vernetzung bewirkte eine merkliche Verbesserung der mechanischen Eigenschaften insbesondere des thermoplastischen Elastomeren.
    Notes: Blends of isotactic polypropylene and EPDM rubber have been treated by electron irradiation in the composition range of rubber modification and in the thermoplastic rubber composition range as well. Mutual crosslinking of the components through the interface could be detected. This intercrosslinking caused a remarkable improvement of the mechanical properties particularly of the thermoplastic rubber.
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  • 56
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    Angewandte Makromolekulare Chemie 175 (1990), S. 205-205 
    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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  • 57
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanisms of photooxidation usually envisaged, are perfected by taking into account photoreactions of peroxy radicals. They involve interaction of a peroxy radical with the polymer to yield a hydroperoxy radical and a pair of macroradicals. After peroxidation, this pair will usually undergo bimolecular termination. The influence of such a reaction on photooxidation kinetics is particularly important for polyethylene. Then, chain termination occurs mainly by interaction of two hydroperoxy radicals or of a hydroperoxy radical with a macroperoxy radical. The reaction does not only affect kinetics of photooxidation but also the nature of the photooxidation products. The latter is more important for polypropylene than for polyethylene.
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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: Isothermal Differential Thermal Analysis was used to test the thermooxidative stability of pipes of polybutene during internal pressure tests at 110°C. At low hoop stresses and long testing times pipe failure was exclusively caused by thermooxidative degradation of the polymer.The stabilizer distribution in the initial state and its alteration during the pressure tests could easily be measured by isothermal DTA. Leaching of antioxidants from pipe walls could be detected. The decrease of residual thermooxidative stability was degressive.Degradation of pipe material started from the exterior pipe wall. Molecular weight of polybutene decreased rapidly after stabilizer exhaustion which could be observed by isothermal DTA.
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  • 59
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A base of experimental data on the ageing of commerial grade plastics is created. In includes assorted physical and chemical properties of plastics and their changes at natural ageing. An automated system for storing and processing of the experimental data is designed. Processing involves mathematical modeling of the changes in properties that aids in empirical prediction. The possibilities of the system are verified with experimental results from a 5-year ageing period of PE-LD and PE-HD. The results show a good agreement between the predicted and real data for selected models.
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  • 60
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    Angewandte Makromolekulare Chemie 179 (1990), S. 35-56 
    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 Morphologie von Polypropylen-Spritzgußteilen mit Bindenaht wurde mit Röntgenweit-und Kleinwinkelstreuung, Lichtstreuung und Polarisationsmikroskopie untersucht. Die erhaltenen morphologischen Daten wurden mit mechanischen Werten aus Zugversuchen korreliert. Es wird gefunden, daß die mechanischen Eigenschaften der untersuchten Proben im wesentlichen von der sphärolithstruktur beeinflußt werden. Anhäufungen von Sphärolithen mit Kristallen der hexagonalen β-Modifikation und eine starke Inhomogenität der Sphärolithstruktur senkrecht zur Bindenaht sind der wesentliche Grund für die verschlechterten mechanischen Eigenschaften. Diese Sphärolithstruktur wird durch die Temperatur des Spritzgußwerkzeugs stark beeinflußt. Die Lamellen-Überstruktur hat dagegen einen vernachlässigbar kleinen Einfluß auf das mechanische Verhalten.
    Notes: The morphology of polypropylene plaques containing a weld line, has been investigated by x-ray wide and small angle scattering, light scattering and polarization microscopy. The results are correlated to mechanical values obtained from tensile tests. While the lamellar morphology is of neglectable influence, it is found, that the mechanical properties of the samples are strongly influenced by the spherulitic structure. Clustering of β-type spherulites and strong morphological inhomogeneities in the vicinity of the weld line are the primary reason for the mechanical weakening of the plaques. The temperature of the mould has a strong effect on the spherulitic structure and thus on the tensile properties of the samples.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 77-85 
    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: Füllstoffe für PVC- und PP-Formmassen wurden mit Mikrowellenplasma behandelt. Photoakustische FT-IR-Spektren zeigen, daß die Plasma-Polymerhülle auf der Füllstoffoberfläche —C=C—, —CH2—, CH3— und andere Gruppen enthält. Aus Röntgenelektronenspektren geht hervor, daß zwischen Siliciumdioxid und der organischen Beschichtung chemische Bindungen existieren. Durch Compoundieren von plasmabehandelten Füllstoffen mit PVC und PP werden Materialien mit guten mechanischen Eigenschaften bei niedrigen Kosten erhalten.
    Notes: Fillers for PVC and PP compounds have been treated by microwave plasma. FT-IR photoacoustic spectroscopy studies show that the plasma polymer sheath on filler's surface contains —C=C—, —CH2—, —CH3 groups, etc. X-ray photoelectron spectroscopy studies reveal that interfacial chemical bondings exist between silica and the organic coating. Application of plasma-treated fillers in PVC and PP compounds gives rise to materials of good mechanical properties and low cost.
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  • 62
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    Angewandte Makromolekulare Chemie 179 (1990), S. 135-148 
    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: Poly-(alkylenadipat)-diole mit Molmassen von 1500, 2000 und 3000 wurden bei Temperaturen von 25 und 60°C in Gegenwart verschiedener Alkohole und unterschiedlicher PUR-Katalysatoren (1,4-Diazabicyclo[2.2.2]octan (DABCO), Dibutylzinndilaurat (DBTL),Dibutylzinndiethoxid (DBTEO) und Dibutylzinnoxid (DBTO)) in Ethylacetat bzw. Toluol gelagert und die Alkoholyse verfolgt. Die erhaltenen Ergebnisse werden mit dem Alkoholyseverhalten verschiedener Dialkyladipate sowie des Lösungsmittels Ethylacetat unter den selben Bedingungen verglichen. Die Alkoholyse verlauft in Gegenwart der zinnorganischen Verbindungen etwa mit gleicher Geschwindigkeit, ohne daß diese selbst signifikant zersetzt werden, wahrend DABCO praktisch inaktiv ist. Die Aktivitat der Alkohole ist starker von ihrer sterischen Struktur als von ihrer Basizitat abhangig. Die Stabilität der Polyalkylenadipate gegenüber einer Umesterung nimmt mit der Lange der Diolalkyleneinheiten des Polyols zu. Die Umesterung von Adipinsäuredialkylestern findet auch partiell in Anwesenheit eines großen Uberschusses an Ethylacetat statt.
    Notes: Poly(alkylene adipate)diols having molar masses of 1500, 2000 and 3000 were stored at temperatures of 25 and 60°C in the presence of low amounts of different alcohols and some polyurethane (PUR) catalysts, such as dibutyltindilaurate (DBTL), dibutyltindiethoxide (DBTEO), dibutyltinoxide (DBTO), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Alcoholysis was studied using either ethyl acetate (EA) or toluene as solvent. The results were compared with those obtained by examining the behaviour of several dialkyl adipates and ethyl acetate under identical conditions. The alcoholysis in the presence of the tin catalysts proceeds at the same reaction rate without significant decomposition of the catalyst, whereas DABCO is practically inactive. The nucleophilic activity of the alcohols depends on their bulk size rather than their basicity. The resistance of polyalkylene adipates to transesterification increases with the increasing alkyl chain length of diol units in polyester. A partial transesterification of dialkyl adipates takes place too, in spite of ethyl acetate being present in excess.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 157-171 
    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 wurde das Permeations- und Trennverhalten von Alkohol/Wasser-Systemen durch poröse PVA-Membranen untersucht. PVA-Membranen mit unterschiedlicher Anzahl und Große von Poren wurden über Mischungen in Lösung mit verschiedenen synthetisierten Polymeren und Copolymeren, wie Polyacrylsäure, Polyacrylnitril, Polyacrylamid, Poly(Methylmethacrylat-co-Maleinsäureanhydrid) etc., anschließendes Gießen von Filmen und Extraktion der Polymeren oder Copolymeren durch Lösungsmittel hergestellt. Die Abhängigkeit der Durchlässigkeit und Trennwirkung von der Größe und Form der permeierenden Moleköle wurde qualitativ diskutiert. Des weiteren wurde die Selektivität der Trennwirkung in Abhangigkeit von der Zusammensetzung von Alkohol/Wasser-Gemischen und von der Größe und Anzahl der Poren untersucht. Es wurde gefunden, daß die Selektivität von der Menge und dem Molekulargewicht der in die Membranen eingebrachten Polymeren abhängt. Wenn der Gewichtsanteil des verwendeten Polymeren größer als 0,1 war, permeierte bevorzugt der Alkoholanteil bei methanolischen Msungen, wobei der Trennfaktor mit steigender Methanolkonzentration anstieg. In Gemischen mit anderen Alkoholen zeigten die Membranen andererseits eine selektive Durchlässigkeit für Wasser. Der Einfluß der Versuchsbedingungen wurde ebenfalls untersucht.
    Notes: The permeation and separation characteristics of alcohol/water systems through porous PVA membranes were investigated. Porous PVA membranes with different pore size and number were prepared by solution blending of PVA with several synthesized polymers or copolymers, such as polyacrylic acid, polyacrylamide, polyacrylonitrile, and methylmethacrylate-co-maleic anhydride, etc. Then casting, and finally extracting the blended polymers or copolymers by solvent from the membranes. The dependency of both permeation and separation on the molecular size and shape of the permeating species was dicussed qualitatively. Moreover, the permselectivity was investigated with attention to the feed composition of alcohol/water mixture and the effect of pore size and number. The selectivity was found to depend on the weight ratio and the molecular weight of polymer introduced to the membrane. When the weight ratio of polymer introduced into the membrane was larger than 0.1, methanol was permeated through membrane preferentially in methanol/water system, and the separation factor increased with increasing the methanol feed concentration. On the other hand, membrane had a selective permeability for water in the other alcohol/water systems. The influence of operating conditions was also studied.
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    Angewandte Makromolekulare Chemie 175 (1990), S. 29-38 
    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: Die Temperatur des T1-Minimums für die Segmentbewegung in Polypropylen, das einen hohen ataktischen Anteil besitzt, ist niedriger als die in isotaktischem Polypropylen. Ein kurzes T1, T1s, tritt bei beiden Materialien auf. Bei Temperaturerhöhung nimmt T2a (T2 der beweglichen amorphen Bezirke) stark und T2m (T2 der dazwischen liegenden Bezirke) leicht zu, während sich T2c (T2 der steifen kristallinen Bezirke) kaum ändert. T2a in Polypropylen mit hohem ataktischem Anteil ist länger als in isotaktischem Polypropylen.Der Massenbruch der kristallinen Bezirke, Fc, nimmt bei Temperaturerhöhung ab und der der amorphen Bezirke, Fa, zu. Die Relaxationsgeschwindigkeit, 1/ (T1min), steigt linear mit Zunahme des amorphen Anteils an, außer bei der mit siedendem n-Heptan extrahierten Probe. Mit Zunahme der Peaktemperatur von tan δ fällt T2a nahezu linear ab, während die Temperatur des T1-Minimums zunimmt.
    Notes: The temperature of the T1 minimum for the segmental motion in polypropylene containing a lot of atactic fraction is lower than that in isotactic polypropylene. A short T1, T1s, appears for both materials. As the temperature is raised, there is a large increase in T2a (T2 of the mobile amorphous regions), and a mild increase in T2m (T2 of the intermediate regions), while there is no substantial change in T2c (T2 of the rigid crystalline regions). T2a in polypropylene containing a lot of atactic fraction is longer than that in isotactic polypropylene.The mass fraction of crystalline regions, Fc, decreases and that of the amorphous regions, Fa, increases as the temperature is raised. There is a linear increase in the relaxation rate, 1/(T1min), as the amorphous fraction is increased, except for the sample extracted with boiling n-heptane. With increase of the peak temperature of tanδ, T2a decreases nearly linearly, while the temperature of the T1 minimum increases.
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    Angewandte Makromolekulare Chemie 180 (1990), S. 191-198 
    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 Bestrahlung von PTFE mit Elektronen niedriger Energie führt zur Abspaltung von Fluor und zum Einbau von Sauerstoff in die Polymeroberfläche. Es wird gezeigt, daß das Ausmaß der Oberflächenveränderungen hauptsächlich von der Zahl und kaum von der Energie der Elektronen abhängt, die die Oberfläche erreichen. Änderungen in der Oberflächenenergie resultieren in unterschiedlichem Benetzungsverhalten. Kontaktwinkelmessungen und Kurvenanalysen der C-1s-Peaks aus Röntgenphotonenspektroskopiemessungen zeigen, daß der am wenigsten benetzbare Teil der bestrahlten Oberflächen in den meisten Fällen aus —CF2 —CF-Einheiten besteht. Werden bei der Bestrahlung nahezu alle Fluoratome abgespalten, bleiben nur isolierte —CF2-oder —CF-Gruppen zurück. Die „receding“-Winkel werden mit zunehmender Sauerstoffkonzentration in der Oberfläche kleiner, was auf die Bildung stark oxidierter Bereiche hinweist. Die Unabhängigkeit der Kontaktwinkel von der Alterungsdauer deutet auf eine sehr geringe Beweglichkeit der Makromoleküle hin, was mit einer starken Vernet-zung an der Oberfläche zusammenhängen könnte.
    Notes: Low energy electron irradiation of PTFE induced fluorine depletion and introduction of oxygen on the surface. The effect on surface chemistry was shown to be dependent mostly on the amount of electrons reaching the sample, rather than on their energy.Changes in surface energy resulted in different wetting behaviors. The measurement of advancing water contact angles and the analysis of XPS C-1s peak shapes showed that the least wettable portion of irradiated surfaces is made in most cases of —CF2—CF — units. When the treatment caused a nearly complete fluorine depletion, only isolated —CF2— or —CF— groups are present. Receding angle values decreased linearly depending on the amount of oxygen introduced on the sample during the treatment, suggesting the formation of strongly oxidized polymer islets. The invariance of contact angles with aging time indicated very low macromolecular mobility, probably related to extensive surface crosslinking.
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  • 66
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    Angewandte Makromolekulare Chemie 181 (1990), S. 41-52 
    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 aqueous dispersions of anionic polyurethanes containing the triethylammonium salt of 2,2-dimethylol propionic acid as chain extender, triethylamine can be largely replaced by ammonia. For electrostatic reasons, NH4+ is namely more tightly bound in the ion pairs located in the Stern layer than NH(C2H5)3+. Thermal treatment of films leads to a loss of base, whereby ammonia is more rapidly released than triethylamine. Therefore, crosslinking with partially methylated hexamethylolmelamine proceeds the faster the more triethylamine is replaced by ammonia.
    Notes: In Dispersionen aus anionischen Polyurethanen, die das Triethylammoniumsalz der 2,2-Dimethylolpropionsäure als Kettenverlängerungsmittel enthalten, läßt sich durch Zugabe von Ammoniak eine weitgehende Verdrängung des Triethylamins erreichen. Aus elektrostatischen Gründen ist nämlich in den in der Sternschen Schicht lokalisierten Ionenpaaren NH4+ fester gebunden als NH(C2H5)3+. Bei der thermischen Behandlung der Filme tritt Basenabspaltung ein, dabei erfolgt die Abgabe von Ammoniak deutlich schneller als die von Triethylamin. Die Spannungswerte der mit teilmethyliertem Hexamethylolmelamin vernetzten Proben sind daher um so höher, je mehr Triethylamin durch Ammoniak ersetzt wurde.
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  • 67
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    Angewandte Makromolekulare Chemie 181 (1990), S. 53-66 
    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: Die Viskoelastizitäts-Parameter von geschmolzenem Polystyrol (PS) wurden mit einem Instron-Kapillarrheometer gemessen.Die Drucknachgiebigkeit B(t) zeigt ein Plateau sowohl im Schmelze (B1)- als auch im Glaszustand (Bg); beide nehmen mit abnehmender Spannung ab. Durch Verschiebung der B(t)-Kurven werden Master-Kurven erhalten, mit denen das Gesamtdruckverhalten (überlagerte elastische und viskose Deformationen) analysiert werden kann. Die stationäre Nachgiebigkeit (Bs) erlaubt eine Beschreibung des elastischen Energieanteils und scheint mit der Extrusions-Strangaufweitung (Bcs/Bds) korreliert zu sein. Die Volumenviskosität (ηk) nimmt mit zunehmender Spannung (P), zunehmender Belastungsgeschwindigkeit (k) und abnehmender Temperatur ab.
    Notes: Viscoelastic parameters of polystyrene (PS) melt in compression creep have been measured in an lnstron capillary-rheometer.Bulk compression creep compliance B(t) shows plateau regions in the molten state (B1) and the glassy state (Bg), both decreasing with increasing stress. Shifting of B(t) curves provides master curves suitable to analysing the total (superposed elastic and viscous deformations) bulk compression behaviour. The steady-state creep compliance (Bs) allows to describe the recoverable elastic energy (Be) and seems to be related to the extrusion die swell (Bcs/Bds). Volume viscosity (ηk) decreases with decreasing stress (P), increasing compression rates (k) and decreasing temperature (T).
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  • 68
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    Angewandte Makromolekulare Chemie 181 (1990), S. 67-74 
    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: Es wurden Untersuchungen über Molekulargewichtsänderungen an physikalisch bei Raumtemperatur gealterten isotaktischen Polypropylenfilamenten (iPP) mit Hilfe der Hochtemperaturgelpermeationschromatographie (HTGPC) durchgeführt. Das Ergebnis der Untersuchungen weist auf eine sehr unbedeutende Änderung des Molekulargewichts des Materials während der Alterung hin.Das Materialgranulat wurde als Bezugsstandard gewählt. Basierend auf der Uneinheitlichkeit D = Mw/Mn des Granulats wurden Filamente der Handelsprodukte GYE 47 und PXC 31399 charakterisiert, deren Alterungsdauer zwischen 2 Wochen und 8 Monaten lag. Bei den Filamenten der Qpe GYE 47 verringerte sich die Breite der Molekulargewichtsverteilung D um durchschnittlich 12%. Andererseits zeigen die Filamente des PXC 31399-vps einen weniger eindeutigen Trend zur Änderung, jedoch im Mittel hat sich die Breite der Verteilung um etwa 20% erniedrigt. Bei letzterem ist die Verteilung iiber die Alterungsdauer stark gestreut. Der GYE 47-Typ zeigt eine nahezu asymptotische Abnahme. Es wird angenommen, daß die Ungleichartigkeit in der Ändenz der Anderung von D zwischen beiden Proben in ihrer unterschiedlichen thermodynamischen Stabilitat liegen ktinnte; PXC 31399 ist weniger stabil.
    Notes: Experiments on the molecular weight variations of physically, room temperature aged isotactic polypropylene (iPP) filaments were done using the High Temperature Gel Permeation Chromatography (HTGPC). Evidence emanating from the studies indicates a very marginal change in molecular weight of the materials during aging.The granules of the materials were chosen as the reference standard. Based on the polydispersity D = Mw/Mn of the granules, filaments of commercial grades GYE 47 and PXC 31399 were characterized between an aging period ranging from 2 weeks to 8 months. The filaments of the GYE 47 grade have their distributions D lowered on the average by about 12%. On the other hand, those of the PXC 31399 grade have a less definite trend in change, but on the average, D is lowered by about 20%. The distributions of this latter grade are highly scattered over the period of aging. The GYE 47 grade shows a reduction in the distribution of a near asymptotic nature. It is believed that the disparity in the trend of change of D between the two samples could be attributed to their relative thermodynamic stability with the PXC 31399 grade being less stable.
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  • 69
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The properties (squared dimensions, anisotropy, numbers of intra- and intermolecular contacts) of a single five-way cubic lattice chain embedded into an environment (matrix) of chains of the same length n = 50 were evaluated as a function of matrix volume fraction (matrix density) v and intermolecular interaction between the matrix polymer and the minority chain segments, characterized by a parameter φ. No convincing evidence was found for the occurrence of a coil-globule transition in the range of matrix densities (v ≤ 0.7) and repulsive interactions between matrix and minority chain (φ ≤ 0.2) investigated. For moderate attractive interaction (φ ≈ -0.17) a compensation of the chaincompressing action of the matrix and the chain-expanding interaction with the matrix was observed resulting in a zero-dependence of the size and shape of the minority chain on matrix density. It further turned out that there are fixed relations among the various size and shape data irrespective of the specific combination of matrix density and thermodynamic interaction by which a particular polymer dimension is produced. These interrelations are fairly the same as those evaluated for isolated chains the size of which is varied by an intramolecular energy parameter φi.
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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
    Notes: New three phases composite materials made of glassbeads as filler, water as liquid dispersed phase and polystyrene as matrix were obtained by polymerization of a water in oil emulsion formed by water dispersed in styrene in which glass beads are added. For this purpose glass beads have to be modified by silanization by a coupling agent 3-(Trimethoxysilyl)propylmethacrylate (TPM) or a silane Octadecyltrichlorosilane (ODMS), in order to prevent the wetting of the glass by water. Only low coverage of the glass surface by the coupling agent (0,05% of TPM) are convenient for the preparation cellular materials having good mechanical properties. At higher coverage ratio, strong hydrophobic glass beads are obtained which destabilize the water / styrene emulsion and lead to macroporous products. Study of the rheology of the filled emulsion appears to be the more simple and more sensitive method to determine the level of wettability of the glass bead by the emulsion which is the most significant parameter for the preparation of such three phases composite materials. Composite materials made of glass beads, air and polystyrene are simply obtained by evaporation of water under vacuum.
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  • 71
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To test the molecular parameters concerning gas sorption in polymers, the concentration of CO2, N2O, CO, N2, CH4 and the noble gases Ne, He in glassy poly(butylene terephthalate) films (PBTP) has been studied gravimetrically with a recording microbalance at 25°C. The sorption isotherms exhibit downward curvature to the pressure axis. As neither solubility nor adsorption can explain the experimental results, analysis was carried out based on the dual-sorption model: gas dissolution and microvoid filling are considered as independent sorption mechanisms. The parameters of the dual-sorption model for the mentioned penetrants are determined. The results indicate that for parameter correlation the Lennard-Jones potential parameters give a rough idea, but size exclusion of gases in small diameter microvoids is proposed and special chemical interactions must be considered.
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  • 72
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    Angewandte Makromolekulare Chemie 185 (1991), S. 283-292 
    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: The ring opening metathesis polymerisation (ROMP) of 5-cyano-2-norbornene with tungsten hexachloride, tungesten oxytetrachloride, bis(dichloralkoxo)tungsten tetrachloride and bis(dichloralkoxo)tungsten oxydichloride as transition metal component was studied. Methylaluminoxan, diethylaluminium ethoxide, tetraisobutyldialuminoxan and tetrabutyltin served as cocatalyst. Toluene, Chlorobenzene and dichloromethane were used as solvents. The concentration of the tungsten components was in the range from 5 × 10-4 to 5 × 10-3 mol/l. Among the catalyst studied, tungsten hexachloride with diethylaluminium ethoxide proved to be the best. The polymerisation was highly selective with this system even at high monomer/tungsten ratios (e.q. 10200:1) and let to high conversions (≥82%).
    Notes: Die ringöffnende metathetische Polymerisation (ROMP) von 5-Cyano-2-norbornen wurde unter Einsatz von Wolframhexachlorid, Wolframoxidterachlorid, Bis(dichloralkoxo)wolframtetrachlorid und Bis(dichloralkoxo)wolframoxiddichlorid als Übergangsmetallkomponente untersucht. Als Cokatalysatoren dienten Methylaluminoxan, Diethylaluminiumethoxid, Tetraisobutyldialuminoxan und Tetrabutylzinn. Als Lösungsmittel wurden Toluol, Chlorbenzol und Dichlormethan verwendet. Die Konzentration der Wolframkomponente lag im Bereich 5 × 10-4 - 5 × 10-3 mol/l. Unter den geprüften Katalysatoren erwies sich Wolframhexachlorid in Verbindung mit Diethylalumiumethoxid als der geeignetste. Mit diesem System verlief die Polymerisation auch bei großen Monomer/Wolfram-Verhältnissen (10200 :1) hochselektiv und führte zu großen Umsätzen (≥82%).
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  • 73
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of dilution on the chain propagation and termination rate constants was investigated in the polymerization of ethyl acrylate in benzene solution at 50°C, with the rotating sector method. The errors of the above rate constants were determined and, by our method applied to decrease these errors, the errors of the propagation rate constant was reduced to its half value. By the application of our earlier results in polymerization kinetics, we found that in this system the chain propagation step is exclusively responsible for the solvent effects observed. Our experimental results can be quantitatively described in terms of the hot redical theory.
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  • 74
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    Angewandte Makromolekulare Chemie 185 (1991), S. 329-334 
    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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  • 75
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    Angewandte Makromolekulare Chemie 174 (1990), S. 1-10 
    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 Photopolymerisation von Ethylenglykoldimethacrylat (EGDMA) mit Methylmethacrylat (MMA) wurde mit Benzoinmethylether (BME) als Initiator in einem Glasrohr durchgeführt, um einen lichtfokussierenden Plastikstab (Radius Rp) mit parabolischer Brechungsindex-Verteilung (Verteilungskonstante A) in der Nähe der Stabachse (bis zum Radius Rc) herzustellen. Die Abhängigkeit von A und Rc/Rp vom Monomerenverhältnis MMA/EGDMA der Ausgangsmischung, der Einfluß der BME-Konzentration auf die Brechungsindex-Verteilung und die Reproduzierbarkeit der Photopolymerisationen wurden untersucht. Das Rc/Rp-Verhältnis stieg mit dem Monomerenverhältnis MMA/EGDMA bei BME = 1,0 Gew.-% und der Geschwindigkeit der UV-Lampe von V = 0,58 mm/min an. Andererseits stieg Rc/Rp bei BME = 0,6 Gew.-% und V = 0,735 mm/min bis zum Monomerenverhältnis von 0,2 an und fiel dann deutlich zwischen 0,20 und 0,25 ab. Die Plastikstäbe, die hier durch Photopolymerisation hergestellt wurden, haben Linseneigenschaften und sind gut reproduzierbar.
    Notes: The photocopolymerization of ethyleneglycol dimethacrylate (EGDMA) with methylmethacrylate (MMA) containing benzoin methyl ether (BME) as initiator was carried out in a glass tube to fabricate a light-focusing plastic rod (radius Rp) with a parabolic refractive index distribution (distribution constant A) in the region near the center axis (radius Rc). The dependence of A and Rc/Rp on MMA/EGDMA feed ratio, influence of BME concentration on the refractive index distribution, and the reproducibilities of the photopolymerizations were investigated. The Rc/Rp increased with the feed ratio used under BME = 1.0 wt.-% at velocity of UV lamp V = 0.58 mm/min. On the other hand, Rc/Rp increased with the feed ratio to 0.2 and then decreased remarkably with the feed ratio in the range of 0.2-0.25 with BME = 0.6 wt.-% at V = 0.735 mm/min. Plastic rods fabricated in the investigation using photopolymerization have lens characteristics and good reproducibilities.
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  • 76
    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: Polystyrol- und Polymethylmethacrylateinzelfäden mit verschiedenen Graden von Doppelbrechung wurden durch die kontinuierliche Änderung der Ziehgeschwindigkeit, der Temperatur der Polymerschmelze und des Molekulargewichts von Polystyrol (PS) und Polymethylmethacrylat (PMMA) gewonnen. Der “brittle to ductile” Übergangspunkt (Übergang des Polymeren vom spröden zum ziehbaren Zustand) wurde für das optisch reine Polystyrol im Bereich der Doppelbrechungszahlen -0,6 · 10-3 bis -2,6 · 10-3 gefunden. Höhe und Lage dieses Punktes werden durch das Molekulargewicht, die Molekulargewichtsverteilung und die Temperatur der Polymerschmelze beeinflußt. Die Werte des Doppelbrechungsindexes von PS sind um zwei Zehnerpotenzen höher als von PMMA. Bei PMMA wurde der “brittle to ductile” Übergangspunkt nicht beobachtet. Die mechanischen und optischen Eigenschaften hängen nicht nur vom mittleren Wert des durch die Doppelbrechung charakteri-sierten Orientierungsgrades ab, sondern auch davon, welcher Teil des Relaxations-spektrums des Polymeren vorzugsweise orientiert ist. Beim Ziehen der PS- und PMMA-Einzelfäden bilden sich in der Mitte des Fadens Risse (crazes), die jedoch nicht an die Oberflache des Fadens treten.
    Notes: Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of -0.6 · 10-3 to -2.6 · 10-3. Both the height and position of this point are influenced by M̄w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.
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  • 77
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    Angewandte Makromolekulare Chemie 174 (1990), S. 105-117 
    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: The possibility of the application of atactic polypropylene is investigated as graft base for the preparation of graft copolymers of vinyl acetate and vinyl chloride respectively graft copolymers from vinyl acetate onto polypropylene as graft base for the preparation of graft copolymers of vinyl chloride in relation to the composition of the original mixture.After compounding of the graft products with polyvinyl chloride or ABS/polyvinyl-chloride mixtures selected mechanical properties are presented in relation to the quantity and composition of the incorporated graft copolymers.
    Notes: Die Möglichkeiten des Einsatzes von ataktischem Polypropylen als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylacetates und Vinylchlorids bzw. von Polypropylen-Vinylacetat-Pfropfprodukten als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylchlorids werden in Abhängigkeit von der Ausgangsgemischzusammensetzung untersucht.Nach Abmischung der Pfropfprodukte mit Polyvinylchlorid bzw. ABS/Polyvinylchlorid-Mischungen werden ausgewählte mechanische Eigenschaften sowohl in Abhängigkeit von der Menge des enthaltenen Pfropfproduktes als auch von der Zusammensetzung der Pfropfpolymerisate dargestellt.
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  • 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: A new spectroscopic method for determining the permeability of ammonia in transparent polymer layers is presented. It is based on the quantitative proof of the ammonia passing the test layer into a sensor layer, containing 4-nitrophenol as an NH3-sensitive probe, which is placed under the test film. The permeability (P) of the test layer is calculated from the slope of extinction with time in the sensor layer. The lag time (t1) gives the diffusion coefficient (D). The suitability of this method is confirmed by comparison with literature values. Diffusion coefficients obtained from t1 correspond well to those obtained by the sorption method.The temperature dependence of P and D in more than five different polymers (CDA, PVB, PVAc, PVC and different polyvinyl alcohols) demonstrates that peculiarities in the temperature dependence of the permeability result from the behaviour of the NH3-solubility (P/D) which is strongly dependent on the polymer structure.
    Notes: Es wird eine neuartige spektroskopische Methode zur Messung der Ammoniak-Permeabilität in transparenten Polymerfilmen vorgestellt. Sie beruht auf dem quantitativen Nachweis des den Testfilm durchdringenden Ammoniaks in einer darunter befindlichen Sensorschicht mit Hilfe der NH3-empfindlichen Sonde 4-Nitrophenol. Aus dem Anstieg der Extinktion mit der Zeit (ΔE/Δt) in der Sensorschicht wird die Permeabilität (P) und aus der Verzögerungszeit (lag time (t1)) der Diffusionskoeffizient (D) berechnet. Die Eignung der Methode wird durch Vergleich mit Literaturwerten belegt. Die aus t1 zugänglichen Diffusionskoeffizienten stimmen sehr gut mit denen überein, die mit der Sorptionsmethode gefunden werden.Die Temperaturabhängigkeiten von P und D in mehr als fünf verschiedenen Polymeren (CDA, PVB, PVAc, PVC und in verschiedenen Polyvinylalkoholen) zeigen, daß Besonderheiten im Temperaturgang der Permeabilität aus dem vom Aufbau des Polymeren stark abhängigen Verhalten der NH3-Löslichkeit (P/D) resultieren.
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  • 79
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    Angewandte Makromolekulare Chemie 179 (1990), S. 99-111 
    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 wurde die strahleninduzierte Pfropfung von 4-Vinylpyridin (VP) auf Styrol-Butadien-Styrol-Copolymere (SBS) in Gegenwart von gelöstem Sauerstoff untersucht. Pfropfcopolymer-Membranen mit unterschiedlichen Pfropfgraden wurden durch Gießen aus benzolischer Lösung hergestellt. Die mechanischen Eigenschaften, die Gaspermeabilität sowie der Einfluß der Temperatur auf die Gasdurchlässigkeit wurden untersucht. Der höchste Pfropfgrad von 8,4% wurde bei einer Bestrahlungszeit von 15,5 herreicht. Sowohl bei kürzeren als auch längeren Bestrahlungszeiten war der Pfropfgrad  -  bedingt durch Störung durch den vorhandenen Sauerstoff  -  niedriger. Reißfestigkeit und Reißdehnung von SBS-g-VP waren vergleichbar rnit SBS. Die Spannungsrelaxation von SBS-g-VP war langsamer als bei SBS, was auf der Bildung von starren Polyvinylpyridin(DVP)-Mikrophasen beruhen könnte, die als permanente Vernetzungspunkte wirken und die Spannungsrelaxation beeinträchtigen könnten.Da SBS eine hohe Gasdurchlässigkeit und PVP eine hohe O2/N2-Selektivität aufweisen, wurde die Gasdurchlässigkeit der Pfropfmembranen untersucht. Die Selektivitat der SBS-g-VP-Membranen stieg mit steigendem Pfropfgrad, allerdings auf Kosten der Permeabilität, Bei Erhöhung der Temperatur nahm die Durchlässigkeit zu, das Verhältnis O2/N2, aber ab. Die Aktivierungsenergie (Ep) der Gasdurchlässigkeit stieg mit dem Pfropfgrad. Für eine nichtgepfropfte SBS-Membran betrug Ep 5,5 kcal/mol für Sauerstoff und 7,2 kcal/mol für Stickstoff. Für eine SBS-g-VP-Membran mit einem Pfropfgrad von 8,4% waren die Ep-Werte für Sauerstoff und Stickstoff 6,5 bzw. 8,1 kcal/mol.
    Notes: The grafting of 4-vinyl pyridine (VP) onto styrene-butadiene-styrene triblock copolymers (SBS) by homografting irradiation with dissolved oxygen was studied. Homograft membranes of various degree of grafting were prepared from a casting solution of grafted copolymer in benzene. The mechanical properties of membranes, gas permeability, and the effect of operating temperature on gas permeation were investigated.The degree of grafting of 8.4% was the largest at an irradiation time of about 15.5 h. It was smaller at both shorter and longer duration because of the interference of dissolved oxygen. It was found that the tensile strength and elongation of SBS-g-VP were similar to those of SBS. The stress relaxation of SBS-g-VP was slower than that of SBS, and this might be due to the formation of rigid microphase separation domain of poly(4-vinyl pyridine), which acted as permanent crosslinking points to reduce the stress relaxation.Using the properties of high flux of SBS and high O2/N2 selectivity of poly(4-vinyl pyridine), the performance of gas permeation of 4-vinyl pyridine homografted SBS membrane was studied. The selectivity of SBS-g-VP membrane increased with increasing degree of grafting. However, it was done at the expense of a decrease in the gas permeability.When the operating temperature of gas permeation increased, the permeability of oxygen and nitrogen increased, and the O2/N2 permeability ratio decreased. The activation energy (Ep) for gas permeation through different degree of grafting of SBS-g-VP membrane (obtained by the Arrhenius law) increased with increasing degree of grafting. For ungrafted SBS membrane, Ep was 5.5 kcal/mol for oxygen and 7.2 kcal/mol for nitrogen. For 8.4% grafting degree SBS-g-VP membrane, Ep for oxygen and nitrogen, were 6.5 and 8.1 kcal/mol, respectively.
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  • 80
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    Angewandte Makromolekulare Chemie 175 (1990), S. 13-27 
    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: The change of molecular mass and long-term strength of high and low density polyethylene under tensile load in surface-active medium was studied. It is shown that long-term strength of polyethylene depends on the molecular mass. The influence of polydispersity on strength was investigated.
    Notes: Es wird über die Untersuchungsergebnisse von Lebensdauer und Molmassenänderung an polydispersen Proben von HDPE und HDPE in einem breiten M̄v-Bereich im Zugversuch in einem oberflächenaktiven Medium berichtet.Die Arbeit enthält auch die Darstellung der quantitativen Änderung der Molmasse von Hochdruck- und Niederdruck-Polyethylen unter Dauerbeanspruchung und die Analyse der Lebensdauer in Abhängigkeit von den unterschiedlichen Molmassen (MM) (M̄w, M̄n, M̄v); die Unterschiede in Abhängigkeit von der Lebensdauer von M̄v für Proben und polydisperse Muster sowie die Vorstellungen über den dualen Einfluß der Polydispersität auf die Lebensdauer mit einer Interpretation der auftretenden Erscheinungen werden beschrieben.
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  • 81
    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: One constitutive property for the description of dyeing polyester-materials with disperse dyes is the particle size distribution in the dye bath. To measure particle sizes below one micrometer in situ, special techniques are required. One of these is the so called photon-correlation-spectroscopy, depending on the scattering of laser light by suspended small particles in a fluid. The mathematical and physical principles of the photon-correlation-technique are explained in this article.
    Notes: Eine zur Beschreibung des Färbevorganges von Polyestermaterialien mit Dispersionsfarbstoffen wesentliche Größe stellt die Partikelgrößenverteilung im Farbebad dar. Partikelgrößen unterhalb eines Mikrometers lassen sich in situ nur mit wenigen Meßtechniken bestimmen. Dazu zählt u. a. die Photonen-Korrelations-Spektroskopie, die auf Streuung von Laserlicht an kleinen, in einer Flüssigkeit suspendierten Teilchen basiert. Die mathematischen und physikalischen Grundlagen dieser Meßtechnik werden in diesem Artikel erläutert.
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  • 82
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    Angewandte Makromolekulare Chemie 175 (1990), S. 81-97 
    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 Kristallinität von Polyethylen, Polyethylenterephthalat und Polypropylen wurde mit Hilfe der Röntgenweitwinkel(WAXS)-und-kleinwinkel(SAXS)streuung gemessen. Die mittels der letzteren Methode erhaltenen Kristallinitätswerte sind deutlich größer als die durch WAXS. Es wird vermutet, daß die Unterschiede mit der Schicht zusammenhängen, die zwischen den amorphen und kristallinen Bereichen liegt. Daraus wurde geschlossen, daß die Röntgenkleinwinkelstreuung nicht als unabhängige Routinemethode zur Kristallinitätsbestimmung angewendet werden kann.
    Notes: The crystallinity of polyethylene, polyethyleneterephthalate, and polypropylene was measured with the aid of wide angle (WAXS) and small angle (SAXS) X-ray scattering methods. The values of crystallinity evaluated using the latter method are distinctly larger than those ones given by the WAXS method. The differences are supposed to be associated with the transition layer existing between the amorphous and crystalline regions. It was concluded that small angle X-ray scattering cannot be employed as an independent routine method of crystallinity determination.
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  • 83
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    Angewandte Makromolekulare Chemie 175 (1990), S. 117-128 
    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: Für das System Cellulosenitrat-μ-Styragel-THF wurde die DP-Ve-Beziehung sowie die Ausarbeitung der betreffenden Eichparameter einer genaueren Betrachtung unterzogen. Die etwa dreißig Eichpräparate waren durch definierten säurekatalysierten Abbau von Baumwollcellulose und anschließende Nitrierung hergestellt worden und umfaßten einen DP-Bereich von 150 〈 DP 〈 8000. Es wird gezeigt, daß mit steigendem DP die DP-Ve-Beziehung drei verschiedene Phasen aufweist. Bei der Anwendung der SEC auf Cellulosenitrat müssen daher bezüglich der Eichung zwei Fehlerquellen in Betracht gezogen werden: eine bezieht sich auf die Methode der Ausarbeitung der Eichparameter als solche, und die andere auf die Nichtbeachtung des Vorhandenseins dreier Abschnitte in der DP-Ve-Beziehung. Die Auswirkung dieser Fehler auf die Genauigkeit der aus den Elutionsdiagrammen abgeleiteten Verteilungskurven und DP-Mittelwerte wird diskutiert.
    Notes: The calibration behaviour of the system cellulose nitrate-μ-Styragel-THF has been studied using about 30 different calibration samples prepared by defined acid catalyzed degradation of cotton cellulose. The samples covered a range of DP between 150 〈 DP 〈 8000. It is shown that the DP-Ve relationship is characterized by the existence of three subsequent stages. Consequently, two sources of errors in the DP-Ve calibration must be taken into consideration. One refers to the methods as such to elaborate the calibration parameters, and the other one arises by neglecting that the DP-Ve relationship involves 3 distinct stages. The extent of the two classes of errors in regard to the exactness of the determined molecular weight averages and molecular weight distributions is discussed.
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  • 84
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    Angewandte Makromolekulare Chemie 175 (1990), S. 141-156 
    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: Bei der Polycondensation von d,l-Asparaginsäure mit Nδ-phthaloyl-L-ornithin in Phosphorsäure bei 185°C entstehen statisticsche Copolymere (Ausbeute 60  -  70%) aus Poly(d,l-succinimid-co-Nδ-phthaloyl-d,l-ornithin), Formel 6, mit inhärenten Viskositäten (DMF) von 5 bis 15 ml g-1. Copolyimide der selben Zusammensetzung 6 und vergleichbarer Kettenlänge werden aus Asparaginsäure und dem Kupferchelat des Phthaloylornithins erhalten. Die Behandlung des Copolymeren 6 mit Hydrazinhydrat fuhrt zur Öffnung der Succinimid-Kettenglieder unter Bildung von Hydrazid-Seitengruppen. Die resultierenden Polyamide sind Poly(α,β-d,l-asparaginsäurehydrazid-co-d,l-ornithin), Formel 7. Kürzere Reaktionszeiten bedingen unvollständige Ringöffnung, und die verbleibenden Succinimid-Gruppen werden bei der folgenden Aufarbeitung hydrolytisch gespalten unter Bildung von Asparaginsaüre-Gruppen; die sogebildeten Polyamide besitzen die Struktur 8. Beide Polymere, 7 und 8, sind in Wasser loslich und zeigen in Wasser inharente Viskositiiten von 5 bis 14 ml g-l. Die Fahigkeit dieser Polyamide zur Arzneimittelverankerung wird durch Ankoppeln von Carbonsau- ren als Modellsubstanzen gezeigt.
    Notes: The polycondensation of d,l-aspartic acid with Nδ-phthaloyl-l-ornithine in phosphoric acid at 185°C gives rise to the formation, in 60  -  75% yield, of random copolymers of the poly(d,l-succinimide-co-Nδ-phthaloyl-D,L-ornithine) type 6 possessing inherent viscosities (DMF) in the range of 5  -  15 ml g-1. Copolyimides of the same compositions 6 and comparable chain lengths are obtained from aspartic acid and the copper chelate of the phthaloylornithine. Treatment of copolymers 6 with hydrazine hydrate in DMF leads to N-deprotection and opening of the intrachain succinimide rings with formation of hydrazide side groups. The resultant polyamides are of the poly(α,β-d,l-asparthydrazide-co-d,l-ornithine) type 7. Shorter reaction periods give incomplete hydrazinolytic ring opening, and the remaining succinimide units are cleaved hydrolytically during the subsequent aqueous workup, thereby transforming into aspartic acid units. The polyamides so formed possess the general poly(α,β-d,l-asparthydrazide-co-α,β-d,l-aspartic acid-co-d,l-ornithine) structure 8 Both types 7 and 8 are soluble in water and, in this medium, give inherent viscosities of 5  -  14 ml g-1. The potential drug-anchoring capabilities of these amine-functionalized polyamides are demonstrated by coupling reactions with model carboxylic acids.
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  • 85
    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: Im Zusammenhang mit Arbeiten über den Wirkungsmechanismus von Antioxidantien in Kohlenwasserstoffpolymeren unter Sauerstoffmangel wurde die Abfangreaktion des Modellradikals 1-Cyano-1-methylethyl (R°) mit N-Isopropyl-N′-phenyl-1,4-phenylendiamin (Ia) und seinem Oxidationsprodukt IIa untersucht. Reines Ia und IIa reagieren kaum mit R′, eine Mischung aus beiden ist jedoch ein effektiver Fänger fur R′, wobei R′ entweder am Stickstoffatom zwischen den aromatischen Ringen unter Bildung von VIa gebunden wird, oder unter Substitution mit dem Phenylenring reagiert, wobei VIIIa entsteht. Verbindung VIa ist labil, bei Vulkanisationstemperatur spaltet sie im neutralen Medium Olefin unter Regenerierung von Ia ab. In Gegenwart von Säuren lauft diese Reaktion auch bei niedrigerer Temperatur ab. Im Produkt VIIIa ist R′ fest gebunden, durch die Nitrilgruppe tritt jedoch eine säurekatalysierte Cyclisierung zum Indolinderivat X ein. Die Bildung von VIIIa ist ein Modell für die Entstehung einer „nichtextrahierbaren Fraktion“ des Antioxidants Ia bei der Stabilisierung von Kohlenwasserstoffpolymeren.
    Notes: In connection with the investigation of the mechanism of antioxidant action of antidegradants in hydrocarbon polymers under the conditions of a relative deficiency of oxygen, scavenging of a model alkyl (1-cyano-1-methylethyl,R°) was studied with Nisopropyl-N′-phenyl-1,4-phenylenediamine (Ia)For abbreviations see p. 11. and its oxidation product, i.e. Nisopropyl-N′-phenyl-1,4-benzoquinonediimine (IIa). While pure Ia and IIa do not react with the radical R° almost at all, their mixture is able to scavenge R° effectively. The reaction is further accelerated with acids. The alkyl R° combines with the antidegradant molecule in two ways, one of which leads to the substitution at the nitrogen atom between the aromatic rings, giving rise to VIa, while the other consists in the substitution of phenylene, leading to VIIIa. The product VIa is labile, and at vulcanization temperatures it readily splits off olefin in a neutral medium, being regenerated to Ia. In the presence of acids this reaction proceeds even at lower temperatures. In the other product, i.e. in VIIIa, the alkyl R° is bound firmly, but due to the presence of the nitrile group, VIIIa is readily cyclized by the effect of acids, and an indoline derivative X is formed. The formation of VIIIa is a model of the formation of an “unextractable fraction” of antidegradant Ia in the stabilization of hydrocarbon polymers. Investigations based on the isolation of reaction products bear at the same time evidence of the possibility of regeneration of an effective antioxidant in the stabilized substrate.
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  • 86
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photochemical degradation of polymers (commonly known as UV degradation) takes place in two stages: First, there is the primary process comprising the rapid formation of radicals caused by quanta of visible light; this involves the dissociation of polymer chain molecules and/or the activation of polymer chain molecules respectively of additives, colorants and impurities contained in the polymer. The secondary process consists in oxidation reactions with singulett-oxygen generated by energy-transfer and/or between the polymer radicals thus formed and adsorbed oxygen, as a result of which gradual degradation of the polymer takes place.An investigation of these individual reactions using a combination of selected physical test methods leads to an unterstanding of the entire reaction sequence involved in photo-oxidative degradation. This knowledge provides a basis for systematically improving the weather-resistance of polymers by modifying their basic polymeric structure or through the controlled use of UV absorbers, quenchers, radical interceptors and antioxidants.The physical test methods themselves are divided into two categories: techniques used for investigating the primary processes (ultra short-time spectroscopy, ESR) and those used to investigate the secondary processes (XPS, FT-IR, UV/VIS et al.).With pigmented polymers, attention is focussed on borderline cases in the use of photoactive and photoinactive pigments: as a result of “photocatalytic oxidation”, photoactive pigments (e.g. TiO2 anatase) lead to additional degradation reactions which take place at the same time as the UV degradation reaction. Photoinactive pigments (e.g. high-grade TiO2-rutile and iron oxide pigments), on the other hand, exhibit negligible or no photocatalytic oxidation and, by absorbing UV radiation, provides better protection for the polymer against UV degradation.This paper gives an overview of the above-mentioned physical methods of investigating primary and secondary photochemical processes, taking a thermoplastic material (Polycarbonate) as an example. A description is also given of the photocatalytic oxidation reations which can take place if pigmented polymers are used, and there is a discussion of the degradation-inhibiting effects of inorganic pigments.
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  • 87
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aim of the present work is to predict the warehouse storage life of polyethylene low-density, polyethylene high-density and polystyrene impact-resistent, using the method of temperature-time superposition. The properties, most representative for thermal ageing, are the relative elongation at break for polyethylene and the impact resistance for polystyrene. The validity of the predicted shelf-life is verified by estimating the change of these properties under real conditions of warehouse storage.
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  • 88
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A commercial type of impact-resistant polystyrene was investigated. Two types of antioxidants, Irganox 245 and Irganox PS-800 were added to polystyrene in ammounts of 0,05 to 0.20%. Films, dumbbells and straight test pieces were subjected to thermal and u.v. ageing. Films of 250 μ thickness were thermally treated at 100°C and separately u.v. irradiated at 360 nm for 24, 72, 120 and 168 hours. Dumbbells and straight test pieces were only thermally aged at 100°C for 7, 14, 21, 28 and 35 days. Mechanical properties were determined. The spectra of samples were recorded using Perkin-Elmer, model 1750 FTIR and Perkin-Elmer data station 7700. Colour changes of all dumbbells were measured using Elrepho apparatus in u.v.-visible region. (Changes of the content of carbonyl and hydroxyl groups, as well as of polybutadiene (PB) unsaturation in films were recorded on i.r. spektrophotometer Perkin-Elmer 257 between 4000 and 625 cm-1 and were published in the first part of this study1).
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  • 89
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    Angewandte Makromolekulare Chemie 181 (1990), S. 85-91 
    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: Formstoffe aus aromatischen Polyepoxiden, aromatischen Polyaminen mit hochtemperaturbeständigen Strukturelementen sowie pulverförmigen Füllstoffen besitzen hervorragende Eigenschaften, wie hohe Glasübergangstemperatur, hohemechanische Festigkeit, kleinen thermischen Ausdehnungskoeffizienten und Schwerbrennbarkeit ohne Zugabe von Flammschutzmitteln. Über die Synthese dieser aromatischen Polyamine, die Herstellung und Verarbeitung der Niederdruckpreßmassen sowie die Eigenschaften der Formstoffe wird berichtet.
    Notes: Moulded materials produced from aromatic epoxide resins, aromatic polyamines with high-temperature-resistant structure units and powdered mineral fillers possess outstanding properties like high glass transition temperatures, high mechanical strength, low linear thermal expansion coefficient, and reduced flammability without the addition of flame retardants. An account is given of the synthesis of aromatic polyamines, the preparation and working of moulding materials and the properties of the finished products.
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  • 90
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    Angewandte Makromolekulare Chemie 190 (1991), S. 1-14 
    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 gemeinsame Reaktion von Benzophenontetracarbonsäuredianhydrid, Maleinsäureanhydrid und Diaminen mit 1,3,5-Triazingruppen wurden niedermolekulare Prepolymere mit Amin-Endgruppen erhalten, die sowohl 1,3,5-Triazingruppen als auch Etherbindungen enthalten. Diese reaktiven Prepolymeren sind in niedrigsiedenden Lösemitteln wie z. B. Chloroform und Tetrahydrofuran löslich. Sie wurden durch Elementaranalyse, IR- und NMR-Spektroskopie, Dampfdruckosmometrie und Viskosimetrie charakterisiert. Beim Erhitzen der Prepolymeren auf Temperaturen zwischen 180 und 190°C tritt Kettenverlängerung durch Michael-Addition auf; gleichzeitig vernetzen sie durch Reaktion der Amin- mit den Maleimid-Endgruppen. Die vernetzten Polymeren sind thermisch stabil; ihr thermisches Verhalten wurde durch TGA, DTA und isotherme Alterung untersucht. Die Biegefestigkeit und interlaminare Scherfestigkeit von aus den Prepolymeren und Carbonfasergeweben hergestellten Laminaten wurden gemessen.
    Notes: Low molecular weight amine-terminated monomaleimide prepolymers containing 1,3,5-triazine groups as well as ether linkages were synthesized by reacting benzophenone tetracarboxylic dianhydride, diamines having 1,3,5-triazine group and maleic anhydride. These reactive prepolymers are soluble in low boiling solvents such as chloroform, tetrahydrofuran etc. They were characterized by elemental analyses, IR and NMR spectroscopy, vapour pressure osmometry, and viscosity. On heating at 180-190°C these prepolymers undergo simultaneous chain extension by Michael addition reaction and crosslinking by mutual reaction between their amine-terminated and maleimide-terminated ends. The cured polymers are thermostable and the thermal behaviour was studied by TGA, DTA, and isothermal aging. Laminates fabricated using these prepolymers and carbon fiber as reinforcing agent were evaluated by their flexural strength and interlaminar shear strength.
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  • 91
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    Angewandte Makromolekulare Chemie 190 (1991), S. 15-32 
    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: Ein Epoxidharz wurde durch Reaktion mit Anilin bzw. Benzylamin in unterschiedlichen molaren Verhältnissen modifiziert. Die modifizierten Harze wurden dann mit Diethylamin und anschließend mit teilblockiertem Toluylendiisocyanat umgesetzt, wobei thermisch vernetzbare Harze mit tertiären Aminen in und am Ende der Polymerkette erhalten wurden. Die partielle Ansäuerung mit Essigsäure lieferte thermisch vernetzbare kationische Harze, aus denen durch Lösen in geeigneten Lösungsmitteln und Zugabe von entionisiertem Wasser Emulsionen hergestellt wurden. Diese wurden hinsichtlich ihrer Eignung zur elektrolytischen Abscheidung untersucht und verglichen. Die Ergebnisse zeigen, daß die Abscheidungsausbeute und das Streuvermögen der Emulsionen aus Benzylamin-modifizierten Epoxidharzen besser sind als die der Anilin-modifizierten Epoxidemulsionen. Ein hohes, vom pH-Wert der Emulsion abhängiges Streuvermögen ist für diese kationischen Harze charakteristisch.
    Notes: Aniline/benzylamine-modified epoxy resins with different molecular weights, which contain tertiary amines in the middle of the polymer chain, were synthesized by the reaction of aniline/benzylamine with epoxy resin at various molar ratios. The resulting aniline/benzylamine-modified epoxy resins were reacted with diethylamine and subsequently reacted with 2-ethylhexanol-blocked toluene diisocyanate to obtain thermally crosslinkable resins which contain tertiary amines at the end and in the middle of the polymer chain. These resins were partially neutralixed with acetic acid to give thermally crosslinkable cationic resins. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The emulsion and electrodeposition properties of these resins were studied in some detail to compare the properties of these cationic resins. The results show that the deposition yields and throwing power of the emulsions prepared from benzylaminemodified epoxy resins are higher than those of the emulsions prepared from anilinemodified epoxy resins. The emulsion having proper pH values can give a high throwing power. High throwing power is the characteristic property of these modified cationic resins. Factors determining the throwing power and deposition yield of the emulsions were also investigated.
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  • 92
    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: Arylacrylsäuren, wie Furylacrylsäure und Thienylacrylsäure können durch Knoevenagel-Reaktion der Arylcarbaldehyde mit Malonsäure in Pyridin dargestellt werden. Durch einfache Veresterung der Arylacrylsäuren in Methanol/Schwefelsäure werden die entsprechenden Arylacrylsäuremethylester mit guten Ausbeuten erhalten. Diese isomerisieren bei Bestrahlung mit UV-Licht (λ ≥ 280 nm) in methanolischer Lösung. Bei der Photoreaktion in Lösung wurde keine Photodimerisierung beobachtet. Die Reaktionskinetik der Photoreaktionen wurde untersucht.
    Notes: Aryl acrylic acids, e. g. furyl acrylic acid or thienyl acrylic acid are readily formed by the Knoevenagel condensation reaction of arylcarbaldehydes and malonic acid in pyridine. Esterification of these acids with methanol/sulfuric acid gives the corresponding aryl acrylic acid methyl esters in good yields. In methanolic solution these methyl esters isomerize upon irradiation (λ 280 nm). No photodimerization was observed. Kinetic data are given.
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  • 93
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    Angewandte Makromolekulare Chemie 190 (1991), S. 67-80 
    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: Different composite materials, with retified or natural poplar and polyester resin were prepared by molding. The influence of the filler granulometry on certain physicochemical (density, humidity, hardness) or mechanical properties of the materials was studied. The density and the increase of mass in humid atmosphere were always found to be less when the wood was thermally treated. On the other hand, the hardness of the composites made from natural poplar was much higher. The mechanical properties were found to be weak when the wood was retified.When the wood was thermally treated, it was possible to optimise the three parameters, namely, density, water retention capacity and mechanical properties. The optimal granulometry of poplar was determined between 0.75 and 1.5 mm.The results obtained are discussed considering the physico-chemical properties of the different varieties of wood studied and the interactions which exist between the polar resin and the wood.
    Notes: Divers matériaux composites à base de peuplier rétifié ou naturel et de résine polyester insaturée ont été préparés par moulage. L'influence de la granulométrie de la charge a été étudiée sur quelques propriétés physico-chimiques (densité, reprise d'humidité, dureté) ou mécaniques des matériaux obtenus. La densité et la reprise de masse en milieu humide sont toujours plus faibles si la charge est traitée thermiquement sous atmosphère inerte. Par contre, la dureté des composites issus du peuplier naturel est plus importante. Les propriétés mécaniques sont inférieures si la charge est rétifitée.Si la charge lignocellulosique est traitée thermiquement, il est possible d'optimiser les trois paramètres: densité, reprise d'eau et propriétés mécaniques; la granulométrie optimale du peuplier est ainsi comprise entre 0,75 et 1,5 mm.Les résultats obtenus sont expliqués en tenant compte des propriétés physico-chimiques des charges et des interactions existant entre la résine polaire et le bois.
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  • 94
    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 vorliegende Arbeit untersucht das Wasserdurchlässigkeitsverhalten von vier Arten verschieden modifizierter Chitosanmembranen zur Abtrennung von Wasser aus wäßrigen Ethanolmischungen. Chitosan wurde aus Chitin von Krebstierschalen durch Verseifung (Deacetylierung) gewonnen. Die in dieser Arbeit untersuchten modifizierten Chitosanmembranen enthielten Carboxymethyl-, Carboxyethyl-, Cyanethyl- und Amidoxim-Chitosan. Die Einführung hydrophiler funktioneller Gruppen in der 6-O Position des Chitosans erhöht die Selektivität der modifizierten Membranen im Vergleich zu den mit Essigsäure komplexierten Chitosanmembranen. Die Untersuchungen zeigen, daß Chitosanmembranen, die Carboxygruppen enthalten, die höchste Wasserdampfdurchlässigkeit aufweisen. Carboxymethyl-Chitosanmembranen zeigen eine maximale Quellung und den höchsten Ethanoldurchfluß bei einer Ethanolkonzentration von ca. 15 Gew.-% im Zulauf aufgrund von Bindungs- und Weichmachereffekten.
    Notes: The present study investigates the pervaporation performance of four kinds of modified chitosan membranes to separate water from aqueous ethanol solution. Chitosan was prepared from chitin abstracted from the crab shell and subsequently deacetylated with aqueous NaOH solution. Modified chitosan membranes examined in this study include carboxymethyl chitosan, carboxyethyl chitosan, cyanoethyl chitosan, and amidoxime chitosan. The incorporation of hydrophilic functional groups into the 6-O position of chitosan enhances the selectivity of modified chitosan membrane compared to the previously reported chitosan-acetic acid complex membrane. Among the modified chitosan membranes, membranes containing carboxy groups show the best pervaporation performance. Carboxymethyl chitosan membranes show the maximum swelling and ethanol flux at approx. 15 wt.-% feed ethanol concentration due to the coupling and plasticizing effect.
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  • 95
    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: The tensile properties of self reinforced poly(propylene)/poly(1-butene) composites, obtained by rapid extension of the melt, have been measured and correlated to morphological parameters derived from x-ray experiments. Critical fiber lengths as a function of sample composition and the elastic modulus and yield stress of the fibers could be determined. It is shown, that, applying a load to the system, the forces are fully taken up by the fibers and the system breaks by fail of the fibers. The longitudinal structure of the fibers is found to be independent of sample composition.
    Notes: Mechanische Parameter wie Elastizitätsmodul, Fliß- und Bruchspannung von aus der hochorientierten Schmelze hergestellten nadelkristallinen Mischungen aus Poly(propylen) und Poly(1-bute) wurden mit morphologischen Parametern, die aus Röntgenmessungen abgeleitet wurden, korreliert. Es wird gezeigt, daß der Elastizitätsmodul des Verbundes aus den E-Moduln der Fasern und der Matrix berechnet werden kann (Mischungsregel). Die an der Probe angreifenden Kräfte werden voll auf die Fasern übertragen; der Verbund kann daher als eigenfaserverstärktes System angesehen werden. Die Abschätzung der kritischen Faserlänge ergibt, daß die Festigkeit der FAsern voll ausgenutzt wird; der Bruch des Systems bei Belastung ist daher auf das Versagen der Fasern zurückzuführen. Das mechanische Verhalten des Verbundes wird stark beeinflußt durch die Komponentenzusammensetzung. Die longitudinale Struktur der Nadeln beider Komponenten bleibt unbeeinflußt von der jeweiligen Co-Komponente.
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  • 96
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 199-211 
    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: Lösliche kationische Polyelektrolyte mit quartären Stickstoffatomen in der Hauptkette wurden durch Polykondensation von Epichlorhydrin (ECH) mit Dimethylamin (DMA) und N,N-Dialkylaminoakylaminen erhalten. Die Reaktionsparameter, die die Polymereigenschaften hauptsächlich beeinflussen, sind: Molverhältnis DMA/asymmetrische Diamine, Ausgangskonzentration der Aminlösung, Molverhältnis ECH/Amine und die Struktur der asymmetrischen Diamine. Das viskosimetrische Verhalten verdünnter wäßriger Lösungen mit oder ohne Zugabe neutraler Salze veranschaulicht die flexible Natur der Polyelektrolyten.
    Notes: Water soluble cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain were prepared via condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and N,N-dialkylaminoalkylamines. The main parameters of the reaction that influence the polymer properties are: DMA/asymmetrical diamine molar ratio, the initial concentration of amine solution, NaOH/amine molar ratio, ECH/amine molar ratio, and asymmetrical diamine structure. The feature of flexible polyelectrolyte own to the investigated polymers was emphasized by the viscosimetric behaviour in dilute aqueous solutions with and without salt presence.
    Additional Material: 6 Ill.
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  • 97
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 213-213 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 98
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 1-11 
    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: Antioxidantien wurden in einer modifizierten Friedel-Crafts-Reaktion mit wasserfreiem Zinkchlorid als Katalysator an Flüssig-Naturkautschuk mit Hydroxy-Endgruppen gebunden. Die immobilisierten Antioxidantien waren weniger flüchtig und extrahierbar als konventionelle Antioxidantien. Sie wurden sowohl einem Latex als auch trockenem Kautschuk zugesetzt; die daraus hergestellten Vulkanisate zeigten eine bessere Alterungsbeständigkeit als Vulkanisate mit konventionellen Antioxidantien.
    Notes: Antioxidants were attached to hydroxy-terminated liquid natural rubber by modified Friedel-Crafts alkylation reaction using anhydrous zinc chloride as catalyst. The rubber bound antioxidants were found to be less volatile and less extractable compared to conventional antioxidants. The bound antioxidants were tried both in latex compounds and dry rubber compounds. The vulcanizates showed improved ageing resistance compared to vulcanizates based on conventional antioxidants.
    Additional Material: 7 Ill.
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  • 99
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 13-20 
    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 Strom-Spannungs-Charakteristik eines Bisphenol-A-Polycarbonats im Span-nungsbereich 50-1000 V und der Einfluß von UV-Bestrahlung (λ = 225 und 300 nm) und Tempern auf die elektrische Leitfähigkeit (σ) des Polycarbonats wurden untersucht. Die Abhängigkeit von σ gegen 1/T deutet auf zwei verschiedene Leitfähigkeits-mechanismen hin. Aus den Ergebnissen wurden die Aktivierungsenergien der Leitfähigkeit und die Sprungdistanzen berechnet.
    Notes: Current-voltage characteristics of polycarbonate samples (PC) have been studied in the voltage range 50-1000 V. The effect of UV-irradiation at λ = 225 and 300 nm, and thermal annealing on the electrical conductivity (σ) of PC was studied. The σ vs. 1/T relationship shows two slopes, i.e. two possible conduction mechanisms. The obtained results made it possible to determine a complete set of conduction parameters including activation energy and jump distance.
    Additional Material: 5 Ill.
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  • 100
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 21-28 
    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 Suspensionspolymerisation wurden Terpolymere aus Acrylnitril (AN), Vinylacetat (VA) (7,5-30 mol-%, bezogen auf AN) und Divinylbenzol (DVB) (10 Gew.-%) hergestellt. Als Verdünner wurden Mischungen von Toluol oder Cyclohexanol (90 Vo1.-%) mit Hexadecan, Octan, Dodecan, 2-Ethylhexanol oder Benzylalkohol (jeweils 10 Vo1.-%) verwendet.Die Porosität der AN-VA-DVB-Terpolymeren ist mit 0,61-0,68 größer als die der entsprechenden AN-DVB-Copolymeren. Die übermolekulare Struktur der Terpolymeren hängt vom verwendeten Verdünner ab, obwohl sich die Porositäten nicht sehr voneinander unterscheiden. Die beim Erhitzen der Terpolymeren auf Temperaturen über 200°C auftretenden thermischen Effekte sind signifikant größer als die bei der Cyclisierung von AN-Polymeren gemessenen.
    Notes: Terpolymers of acrylonitrile (AN), vinyl acetate (VA) (7.5-30 mol-%, related to AN), and divinylbenzene (DVB) (10 wt.-%) were prepared by suspension polymerization. The diluents used were mixtures of toluene or cyclohexanol (90 vol.-%) with solvents (10 vol.-%) such as hexadecane (HD), octane (O), dodecane (D), 2-ethylhexanol (E) or benzyl alcohol (B).It has been found that AN-VA-DVB terpolymers have a higher porosity, about 0.61-0.68, than corresponding AN-DVB copolymers. The terpolymers obtained with mixtures of various diluents differ in their supermolecular structure although they had similar porosity characteristics.The thermal effects accompanying heating of the terpolymers above 200°C significantly exceed that of nitrile groups cyclization observed of the other AN polymers.
    Additional Material: 2 Ill.
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