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  • Articles  (37,745)
  • Humans  (26,747)
  • Physics  (11,018)
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  • 1
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    Physics instruments in the Royal Palace of Naples: from Collection to Museum (2011)
    Accademia di Scienze Fisiche e Matematiche di Napoli
    Details
    Publication Date: 2017-04-04
    Description: This paper aims to trace the documentary history of the Royal Collection of Physics Apparatus,currently housed in the Physics Museum at the Federico II University of Naples...
    Description: Published
    Description: 47 - 59
    Description: 3.10. Storia ed archeologia applicate alle Scienze della Terra
    Description: N/A or not JCR
    Description: reserved
    Keywords: History of Science ; Physics ; Scientific Collection ; Naples ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    If Space is Material, What Inertia Should Be? (2012)
    INGV
    Details
    Publication Date: 2017-04-03
    Description: (extended abstract)
    Description: INGV, Regione Sicilia, Ministero Sviluppo Economico
    Description: Published
    Description: Ettore Majorana Foundation and Centre for Scientific Culture, Erice, Sicily
    Description: 5.9. Formazione e informazione
    Description: open
    Keywords: Inertia ; Physics ; Fluid Dynamics ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Extended abstract
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  • 3
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    Can the history of the ether receive new boost from geosciences? (2020)
    Pavia University
    Details
    Publication Date: 2020-02-10
    Description: A discussion of several kinds of ether as they can be inferred from Geosciences, and what the existence of the ether could imply for Physics and Cosmology. A tribute to the memory of my mentor Franco Selleri.
    Description: This article is written in honor of my mentor Franco Selleri who has helped to consolidate my awareness of the existence of a medium subtended to ordinary matter, and from which everything comes. From my field, the Earth Sciences, come clues converging on an important role of the ether in the geological evolution of Earth and planets, as well as all the structures of the universe. Paleogeographic reconstructions allow a rough quantitative evaluation of the amount of new ordinary matter that is added to the planet in the unity of time, and the consequent statement of some cosmological consequences and on the inner energy balance of the Earth. The concept of central flow of ether defended here is different from the Lorentian stationary ether, but the two concepts could be made compatible.
    Description: SISFA
    Description: Published
    Description: 307-316
    Description: 2TM. Divulgazione Scientifica
    Keywords: Expanding Earth ; History ; Geophysics ; Physics ; Ether flow ; Earth's inner heat balance ; Cosmology ; History and Philosophy of Science
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 4
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    Can humans & coastal landforms co-exist? : proceedings of a workshop held at the Woods Hole Oceanographic Institution, Woods Hole, MA January 24, 2001 (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: The primary objective of this publication is to share with a wider audience the valuable information and extensive dialogue that took place amongst over 140 individuals who attended the second in a series of planned workshops on the science and management of coastal landforms in Massachusetts. This workshop took place at the Woods Hole Oceanographic Institution on January 24, 2001. The individuals who attended this workshop are actively engaged in planning, managing, regulating, engineering, educating, and studying coastal landforms and their beneficial functions. This workshop titled, Can Humans & Coastal Landforms Co-exist?’, was a natural follow-up to a previous workshop, Coastal Landform Management in Massachusetts, held at WHOI October 9-10, 1997 (proceedings published as WHOI Technical Report #WHOI-98-16). The workshop had a very practical, applied focus, providing state-of-the-art scientific understanding of coastal landform function, case history management and regulation of human activities proposed on coastal landforms, a multi-faceted mock conservation commission hearing presented by practicing technical consultants and attorneys that involved all attendees acting as regulators in breakout sessions, and, at the conclusion of the workshop, an open discussion on all issues related to the science and management of coastal landforms, including future research needs.
    Description: Funding for these proceedings was provided by WHOI Sea Grant and the NOAA National Sea Grant College Program Office, Department of Commerce, under NOAA Grant No. M10-2, Woods Hole Oceanographic Institution Sea Grant Project No. NA86R60075.
    Keywords: Coastal ; Landforms ; Humans
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 1574993 bytes
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  • 5
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    Concerns about quadrupole ICP-MS lead isotopic data and interpretations in the environment and health fields (2018)
    MDPI AG
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in International Journal of Environmental Research and Public Health 15 (2018): 723, doi:10.3390/ijerph15040723.
    Description: There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes 208Pb/206Pb and 207Pb/206Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields
    Keywords: Lead isotopes ; ICP-MS ; TIMS ; MC-ICP-MS ; Environment ; Humans ; Rats ; Fractionation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Conceptual models of the climate : 2001 program of studies in geophysical fluid dynamics (2006)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: In 2001, the Geophysical Fluid Dynamics Summer Study Program grappled with Conceptual Models of the Climate. Eli Tziperman (Weizman Institute), Paola Cessi (Scripps Institution of Oceanography) and Ray Pierre- Humbert (University of Chicago) provided the principal lectures. This introduction gave us all a glimpse into the complex problem of the climate, both in the present, past and future, and even on other planets. As always, the next weeks of the program were filled with many seminars from the visitors, and culminated in the fellow's reports.
    Keywords: Climatic changes ; Physics
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 18131236 bytes
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  • 7
    Electronic Resource
    Electronic Resource
    The evolution of two west African populations (1992)
    Springer
    Journal of molecular evolution 34 (1992), S. 336-344 
    Details
    ISSN: 1432-1432
    Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160241
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  • 8
    Electronic Resource
    Electronic Resource
    Phylogenetic evidence for multiple Alu source genes (1992)
    Springer
    Journal of molecular evolution 35 (1992), S. 7-16 
    Details
    ISSN: 1432-1432
    Keywords: Alu source genes ; Humans ; Gorillas ; Retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A member of the young PV Alu sub-family is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160256
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  • 9
    Electronic Resource
    Electronic Resource
    An analysis of codon usage in mammals: Selection or mutation bias? (1991)
    Springer
    Journal of molecular evolution 33 (1991), S. 442-449 
    Details
    ISSN: 1432-1432
    Keywords: Humans ; Mouse ; Rat ; Codon usage ; Mutation bias ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new statistical test has been developed to detect selection on silent sites. This test compares the codon usage within a gene and thus does not require knowledge of which genes are under the greatest selection, that there exist common trends in codon usage across genes, or that genes have the same mutation pattern. It also controls for mutational biases that might be introduced by the adjacent bases. The test was applied to 62 mammalian sequences, the significant codon usage biases were detected in all three species examined (humans, rats, and mice). However, these biases appear not to be the consequence of selection, but of the first base pair in the codon influencing the mutation pattern at the third position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02103136
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  • 10
    Electronic Resource
    Electronic Resource
    The compositional distribution of coding sequences and DNA molecules in humans and murids (1988)
    Springer
    Journal of molecular evolution 27 (1988), S. 311-320 
    Details
    ISSN: 1432-1432
    Keywords: Genome composition ; Coding sequences ; Isochores ; Humans ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02101193
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  • 11
    Electronic Resource
    Electronic Resource
    DNA damage and rpair with age in individual human lymphocytes
    Amsterdam : Elsevier
    Mutation Research DNAging 237 (1990), S. 123-130 
    Details
    ISSN: 0921-8734
    Keywords: Aging ; Humans ; Ionizing radiation ; Single cell electrophoresis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-8734(90)90018-M
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  • 12
    Electronic Resource
    Electronic Resource
    Noninvasive measures of oxidative stress status in humans
    Amsterdam : Elsevier
    Free Radical Biology and Medicine 10 (1991), S. 177-184 
    Details
    ISSN: 0891-5849
    Keywords: Free radicals ; Humans ; Noninvasive analytical techniques ; Oxidative stress status
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0891-5849(91)90073-C
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  • 13
    Electronic Resource
    Electronic Resource
    Evidence for genetic similarity detection in human marriage
    Amsterdam : Elsevier
    Ethology and Sociobiology 6 (1985), S. 183-187 
    Details
    ISSN: 0162-3095
    Keywords: Assortative mating ; Genetic similarity ; Heritability ; Humans ; Kin recognition
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0162-3095(85)90030-5
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  • 14
    Electronic Resource
    Electronic Resource
    Estimating paternity confidence
    Amsterdam : Elsevier
    Ethology and Sociobiology 8 (1987), S. 215-220 
    Details
    ISSN: 0162-3095
    Keywords: Humans ; Paternity confidence ; Relatedness
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0162-3095(87)90045-8
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  • 15
    Electronic Resource
    Electronic Resource
    In vivo loss of telomeric repeats with age in humans
    Amsterdam : Elsevier
    Mutation Research DNAging 256 (1991), S. 45-48 
    Details
    ISSN: 0921-8734
    Keywords: Ageing ; Humans ; Skin cells ; Telomeres
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-8734(91)90032-7
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  • 16
    Electronic Resource
    Electronic Resource
    A neuroheptapeptide influence on cognitive functioning in the elderly
    Amsterdam : Elsevier
    Peptides 1 (1980), S. 55-57 
    Details
    ISSN: 0196-9781
    Keywords: ACTH ; Aging ; Attention ; Cognition ; Humans ; MSH ; Peptide ; Visual retention
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(80)90036-4
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  • 17
    Electronic Resource
    Electronic Resource
    The substance P content of peripheral tissues in several mammals
    Amsterdam : Elsevier
    Peptides 4 (1983), S. 451-455 
    Details
    ISSN: 0196-9781
    Keywords: Biliary system ; Cat ; Guinea-pig ; Humans ; Mucosa ; Rabbit ; Radioimmunoassay ; Respiratory system ; Skin ; Substance P ; Sympathetic nervous system ; Urinary system
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(83)90048-7
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  • 18
    Electronic Resource
    Electronic Resource
    Evidence against autocrine feedback regulation of cholecystokinin secretion in man
    Amsterdam : Elsevier
    Peptides 13 (1992), S. 287-290 
    Details
    ISSN: 0196-9781
    Keywords: Autocrine feedback mechanism ; Cholecystokinin ; Feeding ; Humans ; Radioimmunoassay
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(92)90110-O
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  • 19
    Electronic Resource
    Electronic Resource
    Radioimmunoassay for immunoreactive [des-Leu^1^0]-angiotensin I
    Amsterdam : Elsevier
    Peptides 10 (1989), S. 489-492 
    Details
    ISSN: 0196-9781
    Keywords: Angiotensin II ; Blood ; Humans ; Radioimmunoassay ; Rats ; [des-Leu^1^0]-angiotensin I
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(89)90133-2
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  • 20
    Electronic Resource
    Electronic Resource
    Circulatory effects of VIP in anesthetized man
    Amsterdam : Elsevier
    Peptides 5 (1984), S. 319-323 
    Details
    ISSN: 0196-9781
    Keywords: Blood flow ; Circulation ; Electromagnetic flowmetry ; Humans ; VIP
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(84)90227-4
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  • 21
    Electronic Resource
    Electronic Resource
    Domestic cat predation on vampire bats (Desmodus rotundus) while foraging on goats, pigs, cows and human beings
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 39 (1994), S. 141-150 
    Details
    ISSN: 0168-1591
    Keywords: Cats ; Foraging ; Humans ; Livestock ; Predators ; Vampire bats
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0168-1591(94)90134-1
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  • 22
    Electronic Resource
    Electronic Resource
    Behavioural responses to humans and the productivity of commercial broiler chickens
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 41 (1994), S. 101-114 
    Details
    ISSN: 0168-1591
    Keywords: Fear ; Handling ; Humans ; Poultry ; Productivity
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0168-1591(94)90055-8
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  • 23
    Electronic Resource
    Electronic Resource
    Interspecies homology of cytochrome P-450: toxicological significance of cytochrome P-450 cross-reactive with anti-rat P-448-H antibodies in liver microsomes from dogs, monkeys and humans
    Amsterdam : Elsevier
    Mutation Research Letters 226 (1989), S. 163-167 
    Details
    ISSN: 0165-7992
    Keywords: Cytochrome P-450 ; Dogs ; Humans ; Monkeys ; P-448-H ; Rats
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0165-7992(89)90014-6
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  • 24
    Electronic Resource
    Electronic Resource
    Elevated frequencies of hprt mutant lymphocytes in cigarette-smoking mothers and their newborns
    Amsterdam : Elsevier
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 304 (1994), S. 285-294 
    Details
    ISSN: 0027-5107
    Keywords: Cotinine ; Genetic monitoring ; Hprt mutation ; Humans ; Lymphocytes ; Pregnancy ; Smoking ; Tobacco
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0027-5107(94)90221-6
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  • 25
    Electronic Resource
    Electronic Resource
    Thermal gradients in the oesophagus of man during exercise and passive warming
    Amsterdam : Elsevier
    Journal of Thermal Biology 5 (1980), S. 249-251 
    Details
    ISSN: 0306-4565
    Keywords: Humans ; exercise ; hyperthermia ; oesophageal temperature
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0306-4565(80)90029-7
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  • 26
    Electronic Resource
    Electronic Resource
    Atoms to astronomy: Computer graphics at the Jet Propulsion Laboratory (1986)
    Springer
    The visual computer 2 (1986), S. 159-163 
    Details
    ISSN: 1432-2315
    Keywords: Education ; Animation ; Computer graphics ; Physics ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Within the Jet Propulsion Laboratory in Pasadena, California, state of the art computer graphics animation is done in the Computer Graphics Laboratory. The topics of the animations cover many scientific disciplines. Specific features of the system developed there, both hardware and software, are discussed. The prime mover of the effort is Dr. James F. Blinn of Pasadena; his role and experiences are elaborated. Their current largest project is The Mechanical Universe; the system is used for its production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01900326
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  • 27
    Electronic Resource
    Electronic Resource
    The solar wind and human birth rate: A possible relationship due to magnetic disturbances (1990)
    Springer
    International journal of biometeorology 34 (1990), S. 42-48 
    Details
    ISSN: 1432-1254
    Keywords: Briths ; Humans ; Solar wind ; Geomagnetism ; Melatonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Data obtained from the literature on the annual pattern of human conceptions and plasma melatonin at high latitudes indicated that simple annual rhythms do not exist. Instead, prominent semiannual rhythms are found, with equinoctial troughs and solsticial peaks. A prominent semiannual environmental event is the magnetic disturbance induced by the solar wind. The semiannual magnetic disturbances are worldwide, but most pronounced in the auroral zones where the corpuscular radiation enters the atmosphere. Magnetic indices that predominantly reflect these events were obtained from the literature and correlated with the melatonin and conception data. Significant and inverse correlations were found for Inuit conceptions and the melatonin data. The correlations obtained for 48 contiguous states of the United States indicated that only the extreme northern states exhibited this relationship. These data were compared with a previous correlational study in the United States which established that sunshine was correlated with conceptions in the middle latitude and southern states. An hypothesis of dual control by electromagnetic and magnetic energies is proposed: melatonin is a progonadal hormone in humans controlled by both factors, depending on their relative strength. Other studies are reviewed regarding the possible factors involved in determining the annual pattern of human conceptions. Demographic studies of geographic variation in temporal patterns of conceptions, with particular regard to variations of the magnetic fields on the earth's surface, may provide some insight into the efficacy of these different factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01045819
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  • 28
    Electronic Resource
    Electronic Resource
    Perception of shape from shading in chimpanzees (Pan troglodytes) and humans (Homo sapiens) (1998)
    Springer
    Animal cognition 1 (1998), S. 25-35 
    Details
    ISSN: 1435-9456
    Keywords: Key words Shape from shading ; Visual search ; Texture segregation ; Chimpanzees ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100710050004
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  • 29
    Electronic Resource
    Electronic Resource
    Agaricus Bisporus: An assessment of its carcinogenic potency (1993)
    Springer
    Mycopathologia 124 (1993), S. 73-77 
    Details
    ISSN: 1573-0832
    Keywords: Assessment ; Cancer ; Humans ; Hydrazines ; Mushroom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This assessment focuses on the concentrations of some chemicals present in theAgaricus bisporus mushroom, the cancer-inducing doses of these chemicals or mushroom used in the animal experiments, the total amounts of these chemicals or mushroom needed to induce cancer in these mice, and the estimated total amounts of these chemicals or mushroom needed to induce cancer in humans. By adding the estimated amounts of chemicals needed to induce cancer and by comparing it with the amount of raw mushroom needed to induce the same effect, it becomes obvious that we have accounted for less than 2% of the carcinogenic components of theAgaricus bisporus mushroom. Since some unavailable data handicapped this assessment, it should be regarded as tentative and subject to further adjustment.
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    Calcium phosphates in pharmaceutical tableting (1993)
    Springer
    Pharmacy world & science 15 (1993), S. 105-115 
    Details
    ISSN: 1573-739X
    Keywords: Calcium phosphates ; Drug compounding ; Excipients ; Particle size ; Physics ; Powders ; Tablets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ten commercially available calcium phosphates used for direct tableting were evaluated. The particle size distributions, powder properties, Sorption isotherms and pH values of aqueous slurries were compared. All samples showed good or at least sufficient flowability. Scanning electron micrographs illustrated the different kinds of manufacturing and gave hints on their expectable behaviour under compaction pressure. The sorption isotherms of identical chemical substances, which had been manufactured by different methods, differed strongly. This can be related to their specific surface areas. Most of the hydroxylapatites have large surface areas and can absorb up to more than 15% water at 93% relative humidity. Dibasic calcium phosphate dihydrate was non-hygroscopic and absorbed less than 1% water. With the exception of monobasic calcium phosphate monohydrate all calcium phosphates behaved quite neutral in water. Monobasic calcium phosphate monohydrate can be regarded as a solid acid. Although the calcium phosphates are usually stable substances, the role of crystal water in the case of dibasic calcium phosphate dihydrate and monobasic calcium phosphate monohydrate is problematic due to possible interactions with active ingredients.
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    Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 489-499 
    Details
    ISSN: 1573-9686
    Keywords: Work of breathing ; Inspiratory pressure-time integral ; Respiratory modeling ; Dogs ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work ( $$\dot W$$ ) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while $$\dot W$$ was found to increase slowly with frequency above its optimum. In contrast, both $$\dot W$$ and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the $$\dot W$$ criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.
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    Implementation of periodic acid-thiosemicarbazide-silver proteinate staining for ultrastructural assessment of muscle glycogen utilization during exercise (1985)
    Springer
    Cell & tissue research 242 (1985), S. 229-232 
    Details
    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Ultrastructure ; Exercise ; Glycogen ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Distribution of glycogen particles in semithin and ultrathin sections of biopsy samples from human muscles subjected to either short- or long-term running were investigated using PAS and Periodic Acid-ThioSemiCarbazide-Silver Proteinate (PA-TSC-SP) staining methods. Glycogen particles were predominantly found immediately under the sarcolemma or aligned along the myofibrillar Iband. After long-term exhaustive exercise type-1 fibers with a few or no glycogen particles in the core of the fibers were frequently observed. The subsarcolemmal glycogen stores of these “depleted” type-1 fibers were about three times as large as after exhaustive short-time exercise. Another indication of utilization of subsarcolemmal glycogen stores during anaerobic exercise was that many particles displayed a pale, rudimentary shape. This observation suggests fragmental metabolization of glycogen. Thus, depending on type of exercise and type of fiber differential and sequential glycogen utilization patterns can be observed.
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    Mechanical properties and structure relationships in drawn fibers of elastomer-polyoxymethylene blends (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 107-118 
    Details
    ISSN: 0887-6266
    Keywords: polyoxymethylene ; elastomer blend ; drawn fibers ; mechanical properties ; structure relationships ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Superdrawn fibers of an elastomer-poly(oxymethylene) (POM) blend have been prepared and investigated in terms of the structure and mechanical properties. The development of the mechanical properties along the fiber axis and the formation of a higher order structure during drawing were slightly retarded by blending, but the loop tenacity increased greatly with the elastomer content. The blend microtextures had an immiscible and phase-separated morphology in which the elastomer was dispersed in the form of streaks between the oriented POM layers, which allowed the fiber to split into smaller filaments on bending. The high loop tenacity of the blend fibers is due to an increase in the radius of curvature resulting from the filament splitting on bending, because the shear stress at the bending corner becomes higher as the radius of curvature increases. © 1997 John Wiley & Sons, Inc.
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    Fluorimetry and differential scanning calorimetry analysis of ionomers with low Eu3+ contents (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 101-106 
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    ISSN: 0887-6266
    Keywords: europium methacrylate ; ionomers ; fluorimetry ; differential scanning calorimetry ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fluorimetry and differential scanning calorimetry have been used to characterize ionomers that were synthesized by copolymerization of methyl methacrylate, methacrylic acid, and europium methacrylate (EMA). Under excitation of UV light at 375 nm no self-quenching was found in fluorescence of EMA-containing ionomers at 615 nm within the Eu3+ concentration range of 1.6 × 10-2 to 11.49 × 10-2 mol %, which means that the distance between two Eu3+ ions is larger than 50 Å. In the same concentration range self-quenching took place in europium octanoate (EOA)-containing ionomers in which EOA was doped as an additive. Only one Tg was found for both kinds of polymers within the concentration range of Eu3+ ions. For all ion contents studied, Tg values were essentially independent of ion content and values were slightly higher for the EMA containing ionomers. © 1997 John Wiley & Sons, Inc.
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    Toughening of a trifunctional epoxy system: IV. Dynamic mechanical relaxational study of the thermoplastic-modified cure process (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 153-163 
    Details
    ISSN: 0887-6266
    Keywords: epoxy resin ; thermoplastic ; dynamical mechanical spectroscopy ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical spectroscopy has been used to investigate the cure of a thermoplastically modified trifunctional epoxy resin. The complex dissolution, curing behavior, and variations in the glass transition of the thermoplastic (PSF) phase were described, as was the Tg behavior of the epoxy phase. Prereaction of the PSF material with the epoxy resin was found to greatly increase the solubility of the PSF in the epoxy phase with little effect on the concentration of the epoxy monomer dissolving in the PSF phase. The curing behavior of the epoxy component in the thermoplastic phase was also investigated, in addition to changes in the mobility of the network at both gelation and vitrification. © 1997 John Wiley & Sons, Inc.
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    Vapor sorption in emptied clathrate samples of syndiotactic polystyrene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 133-140 
    Details
    ISSN: 0887-6266
    Keywords: syndiotactic polystyrene ; polymorphism ; chloroform ; clathration ; sorption ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The analysis of chloroform vapor sorption at 35°C in semicrystalline syndiotactic polystyrene samples shows remarkably different sorption isotherms, depending on the crystalline form of the samples. In particular, “emptied” clathrate (“emptied” δ form) samples are characterized by higher equilibrium sorption levels and the differences are particularly relevant for low vapor activities. Moreover, sorption kinetics detected at a vapor activity equal to 0.5 show that in the case of “emptied” δ form samples the sorption rate is much higher than for the other semicrystalline samples. The larger sorption equilibrium uptakes and sorption rates of the “emptied” δ form samples are essentially due to their ability to absorb chloroform, already for low activities, by clathration in the crystalline phase. The measured equilibrium uptakes and sorption kinetics suggest that “emptied” δ form samples of syndiotactic polystyrene could be suitable for removing polluting chlorinated compounds from vapor and liquid streams. © 1997 John Wiley & Sons, Inc.
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    Synthesis and dilute solution properties of divinylbenzene-linked polystyrene stars with mixed arm lengths: Evidence for coupled stars (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 141-151 
    Details
    ISSN: 0887-6266
    Keywords: Asymmetric star polystyrenes ; star polymers ; solution properties ; size exclusion chromatography ; light scattering ; viscometry ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sequential anionic polymerization of styrene and divinylbenzene (DVB) is known to lead to the formation of star-shaped polymers. This ‘arms-first’ method has been widely used and studied. It is known that this polymerization forms stars with anionically active cores. This article is concerned with the attempt to make asymmetric-star polymers utilizing these living carbanionic sites present in the core to form a second set of shorter arms growing out from the star core. The presence of remaining unreacted DVB within the core was found to cause the stars to couple to form linked double stars and other larger structures. Results from detailed dilute solution studies of the resulting polymers are reported. It was found that the results obtained from size exclusion chromatography for the double stars were flow rate dependent; only at low flow rates was a true size separation obtained. © 1997 John Wiley & Sons, Inc.
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    Electropolymerization rates of polythiophene/polypyrrole composite polymer with some dopant ions (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 165-172 
    Details
    ISSN: 0887-6266
    Keywords: polythiophene ; polypyrrole ; electropolymerization ; dopant anion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pyrrole, thiophene, and a mixture of the two monomers were electrochemically polymerized to investigate polymerization rates and the morphology change of the polymer matrix, and to improve the aging and cyclic voltammetric behaviors of the polymers. Thiophene was polymerized on a smooth surface of Pt electrode by two steps. The first step was controlled by electron transfer at the electrical double layer and the other by diffusion of the monomer reacting on the immobilized layer consisting of the precoated thiophene polymer. The electropolymerization rate of the second step was 1.85 × 10-4 cm3 mol-1 s-1, which is faster by 8.63 × 102 times than the first step. Some supporting electrolytes such as KPF6, LiClO4, TBAP, and TBABF4 were employed in the polymerization reaction to see the effects of dopant anions on the polymerization rate, and KPF6 was the fastest one at 2.41 × 10-6 cm s-1. However, owing to its sensitivity to oxygen, LiClO4 was used for the polymerization that is fairly stable in air and the same rate as KPF6. For the competitive polymerization reaction of the two monomers the rate of thiophene was found to be about 11 times slower than that of thiophene alone. When the starting concentration of the thiophene monomer was higher than pyrrole by five times, its portion in the composite polymer was found to be only 8-10%. However, this level gave desirable results in terms of redox properties and aging. The resistance against aging was explained by the morphology change, which came from great shrinking of its porosity. © 1997 John Wiley & Sons, Inc.
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    Dielectric relaxation of LC-thermotropic poly(ester imide)s (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 203-212 
    Details
    ISSN: 0887-6266
    Keywords: poly(ester-imide)s ; liquid crystalline polymers ; dielectric relaxation ; model calculations ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two different series of poly(ester imide)s, which are distinguished from each other in the orientation of the ester linkages and show well-differentiated thermotropic behavior, are investigated by means of model calculations and dielectric relaxation spectroscopy. Model calculations show that the orientation of the ester linkages has a strong influence on the rotational energy barriers. The dielectric relaxation spectra of both series shows three relaxation regions in the temperature range between 100 and 400 K that have been identified as the α-, β- and γ-relaxation processes. A difference of about two orders of magnitude between the characteristic rates of the γ-relaxation is the main feature observed in the dielectric response. However, the β-relaxation shows very similar behavior for both series. The differences in the relaxation behavior in the solid state are interpreted on the basis of the rotational barriers deduced from the model calculation results. © 1997 John Wiley & Sons, Inc.
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    Relaxations of confined chains in polymer nanocomposites: Glass transition properties of poly(ethylene oxide) intercalated in montmorillonite (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 59-67 
    Details
    ISSN: 0887-6266
    Keywords: nanocomposites ; glass transition ; confined chains ; intercalation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relaxation behavior of poly(ethylene oxide) (PEO), intercalated in montmorillonite, a naturally occurring mica-type silicate, was studied by differential scanning calorimetry (DSC) and thermally stimulated dielectric depolarization (or thermally stimulated current, TSC). The materials were synthesized by melt or solution-mediated intercalation. In both intercalates, the PEO chains were confined to ca. 0.8-nm galleries between the silicate layers. The solution intercalate contained a fraction of unintercalated PEO chains which exhibited a weak and depressed PEO melting endotherm in DSC. In contrast, the melt intercalate was “starved” such that almost all the PEO chains were effectively intercalated. For these melt intercalates, no thermal events were detected by DSC. TSC thermal sampling technique was used to examine the glass transition regions and to estimate the extent of cooperativity of chain motions. The motions of the intercalated PEO chains are inherently noncooperative relative to the cooperative Tg motions in the amorphous portion of the bulk polymer. This is presumably due to the strong confining effect of the silicate layers on the relaxations of the intercalated polymer. © 1997 John Wiley & Sons, Inc.
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    Physical aging of poly(ether sulfone)-modified epoxy resin (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 69-83 
    Details
    ISSN: 0887-6266
    Keywords: epoxy resin ; poly(ether sulfone) ; physical aging ; DSC ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The physical aging process of 4,4′-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with poly(ether sulfone) (PES) was studied by differential scanning calorimetry (DSC) at four aging temperatures between Tg-50°C and Tg-10°C. At aging temperatures between Tg-50 and Tg-30°C, the experimental results of epoxy resin blended with 20 wt% of PES showed two enthalpy relaxation processes. One relaxation process was due to the physical aging of PES, the other relaxation process was due to the physical aging of epoxy resin. The distribution of enthalpy relaxation process due to physical aging of epoxy resin in the blend was broader and the characteristic relaxation time shorter than those of pure epoxy resin at the above aging temperatures (between Tg-50 and Tg-30°C). At an aging temperature between Tg-30 and Tg-10°C, only one enthalpy relaxation process was found for the epoxy resin blended with PES, the relaxation process was similar to that of pure epoxy resin. The enthalpy relaxation process due to the physical aging of PES in the epoxy matrix was similar to that of pure PES at aging temperatures between Tg-50 and Tg-10°C. © 1997 John Wiley & Sons, Inc.
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    Gas permeation and sorption studies on stereoregular polynorbornene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 91-99 
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    ISSN: 0887-6266
    Keywords: polynorbornene ; gas separation ; membranes ; permeation ; sorption ; ring-opening metathesis polymerization ; ROMP ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Advances in the field of membrane gas separation over the past decade have encouraged the search for even better polymers and membranes for gas separation. They also have motivated studies on the relationship between the structure and the gas transport properties of different classes of polymers. Interest has recently been demonstrated in the literature in norbornene polymers with different side groups. These polymers can easily be prepared via ring-opening metathesis polymerization (ROMP) of norbornene (bicyclo[2.2.1]hept-2-ene) derivatives. So far, information on the microstructure of the polymers is scarce, so little is known about the influence of stereochemistry and tacticity of the polymer on gas separation properties. In this work, we present gas permeability and selectivity data for stereoregular unsubstituted polynorbornene. It will be shown that a high order of tacticity has a positive effect on both permeation and separation results. © 1997 John Wiley & Sons, Inc.
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    Gas permeation properties of blend and copolymer membranes composed of 1-trimethylsilyl-1-propyne and 1-phenyl-1-propyne structures (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 119-131 
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    ISSN: 0887-6266
    Keywords: PMSP ; copolymer and blend ; aging ; gas permeability ; molecular motion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The poly(1-trimethylsilyl-1-propyne) (PMSP) has the potential to be an important membrane gas separation material due to the fact that it has the highest gas permeability of all polymeric membranes. One problem with PMSP is a decrease in the gas permeability with age. In order to understand the aging processes, we studied the change in free volume and the molecular motions of the PMSP and its membranes modified with 1-phenyl-1-propyne (PP) structures; that is, a copolymer and a blend of PMSP and PPP. During aging, the unrelaxed volume of the PMSP membrane was relaxed, and the molecular motion of carbons dropped, suggesting that the decrease in the microvoids caused a tighter chain packing. The copolymer and blend membrane had stable permeability compared to the PMSP. In particular, the addition of a small amount of the PP structure provided excellent stability with high gas permeability. A decrease in the unrelaxed volume of modified membranes was hardly observed with age; however, the molecular motion of some carbons slightly changed. This change did not affect the gas permeability. In this case, a larger unrelaxed volume was probably a dominant factor in the gas permeation of the PMSP rich membranes relative to the molecular motion in the T1 measurement. © 1997 John Wiley & Sons, Inc.
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    Non-Kramers' behavior of the chain local dynamics of PVC in dilute solution. Carbon-13 NMR relaxation study (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 317-329 
    Details
    ISSN: 0887-6266
    Keywords: PVC ; chain local dynamics ; 13C NMR relaxation ; Kramers' theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Carbon-13 spin-lattice, spin-spin relaxation times, and NOE values were measured as a function of temperature at two magnetic fields for poly(vinyl chloride) (PVC) in three solvents: chloroform, dioxane, and dimethyl sulfoxide. The relaxation data were interpreted in terms of chain local motions by using the bimodal time-correlation function of the Dejean-Laupretre-Monnerie (DLM) model. Using this model, the correlation times obtained in this study, as well as those from an earlier study in dibutyl phthalate and 1,1,2,2-tetrachloroethane did not follow a linear relationship with solvent viscosity. Instead, the chain local dynamics showed a 0.60 power dependence on solvent viscosity, indicating that PVC deviates from the hydrodynamic Kramers' theory. © 1997 John Wiley & Sons, Inc.
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    Neutron structure analysis of poly(vinyl alcohol)This paper was partly presented in the International Conference of Neutron Scattering, Sendai, Japan, 1994 and in the 5th SPSJ International Polymer Conference, Osaka, Japan, 1994. (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 193-198 
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    ISSN: 0887-6266
    Keywords: neutron diffraction ; X-ray diffraction ; poly(vinyl alcohol) ; rigid-body least-squares method ; difference synthesis ; intramolecular hydrogen bond ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Different crystal structure models have been proposed for atactic poly(vinyl alcohol) by two groups: Bunn and Sakurada et al. The models differ principally in the azimuthal angle of the planar zigzag backbone and the hydrogen bonding network. In the present study, reexamination of the crystal structure analysis was carried out by using both the X-ray and neutron diffraction methods. The crystal structure model proposed by Bunn is found to be superior. The (Fo - Fc) synthesis was made for the neutron data (100 K), in which the hydrogen atoms to be associated with the hydrogen bonds are not incorporated into Fc calculation. On the map, three peaks were found, which may be attributed to the hydrogen atoms to be associated with the intramolecular hydrogen bonds between OH groups in an isotactic sequence and the two kinds of intermolecular hydrogen bonds. © 1997 John Wiley & Sons, Inc.
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    The effect of molecular weight and crystallite structure on yielding in ethylene copolymers (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 213-223 
    Details
    ISSN: 0887-6266
    Keywords: stress-strain ; yield ; crystallite ; ethylene copolymer ; superstructure ; lamellae ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nominal stress-strain curves of a series of random ethylene-hexene copolymers having narrow composition and most probable molecular weight distributions were investigated. A series of such molecular weight copolymers with a constant concentration of branches were crystallized under a variety of conditions. In each molecular weight series the level of crystallinity was approximately constant. Particular attention was focused on the yield region and the nature of the yielding process. It was found, quite surprisingly, that the yield stress was not solely dependent on the crystallinity level. Moreover, the shape of the force-elongation curve in the yield region was very dependent on the molecular weight and the crystallization mode. These changes in yielding correlated quite well with the overall crystallite structure that was characterized by thin section transmission electron microscopy. The orthorhombic unit cell of polyethylene was maintained in all the samples despite the changes that occurred in the overall crystallite structure. © 1997 John Wiley & Sons, Inc.
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    Synthesis and properties of sulfonated polyurethane ionomers with anions in the polyether soft segments (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 225-232 
    Details
    ISSN: 0887-6266
    Keywords: polyurethane ionomer ; transesterification ; morphology ; phase compatibility ; ionic cluster ; solid-state ionic conductivity ; single ion transport mechanism ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of polyether (PTMO, PEO) polyurethane ionomers having different contents of sodium sulfonate groups in the soft segments have been synthesized. The reaction of transesterification was involved in the incorporation of the sodium sulfonate groups in the polyether. The polyurethane ionomers were characterized by means of dynamic mechanical thermal analysis, differential scanning calorimetry, and small-angle x-ray scattering. Solid-state ionic conductivity was also measured. As the ionization level increased, the compatibility of the hard and soft segments increased and the glass transition region of the soft segment became broader. These samples had relatively higher moduli and good film-forming ability. Moreover, this kind of ionomer provides a very promising ionic conductive multiphase polymer with a single ion transport mechanism. © 1997 John Wiley & Sons, Inc.
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    The effect of highly specific lattice hydrogen bonding on morphologies of solution-grown crystals (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1175-1183 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; morphology ; chain folding ; lamella ; hydrogen bonding ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphologies of solution-grown crystals in systems containing strong and specific intralattice hydrogen bonding (nylons) are compared with systems displaying only van der Waals intracrystal attractions. The latter are shown to produce crystals that clearly mirror the underlying crystallographic symmetry; in the former systems the morphologies are much more complex and disorganized. This difference is discussed in terms of intralattice forces affecting growth rates and chain rearrangement during crystallization. Arguments deriving from differences in lamellar thickening behavior are also used to demonstrate this point. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1175-1183, 1997
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    Polymer-polymer interactions via analog calorimetry. 2. Blends of polystyrene with bisphenol-A polycarbonate and tetramethyl bisphenol-A polycarbonate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 489-505 
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    ISSN: 0887-6266
    Keywords: polymer blends ; analog calorimetry ; heat of mixing ; mean-field binary interaction model ; polystyrene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Analog calorimetry is used as a tool to study the interaction of polystyrene, PS, with bisphenol-A polycarbonate, PC, and with tetramethyl bisphenol-A polycarbonate, TMPC. Electrostatic charge calculations were used as a guide to divide polymer repeat units and analogs into groups. A mean-field binary interaction model was used to evaluate group interaction energies. The enthalpic interaction energy obtained from this study for the PS-PC pair is 0.41 ± 0.13 cal/cm3 while that for the PS-TMPC pair is 0.19 ± 0.34 cal/cm3. The result for PS-PC blends is in good agreement with values obtained from studies using the critical molecular weight approach and the phase behavior of copolymer blends. The value for PS-TMPC does not correctly predict the phase behavior of this blend; however, its standard deviation (on both an absolute and relative basis) is large and the range of possible interaction energies includes the negative values obtained from neutron scattering. The results of this study indicate that the presence of methyl groups on the aromatic ring of TMPC repeat unit is the main factor favoring the miscibility of PS-TMPC blends. © 1997 John Wiley & Sons, Inc.
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    Elastic behavior of chitosan films (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 517-521 
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    ISSN: 0887-6266
    Keywords: elasticity ; chitosan ; biopolymer ; stress-strain ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermoelastic behavior and equilibrium stress-strain properties of chitosan films lightly crosslinked with gluteraldehyde and swollen with water were studied. Precautions were taken to preclude changes in the swelling ratio of swollen sample films during the experiment. The results indicate that at relatively low extensions the elastic behavior of the biopolymer is entropic in origin. The equilibrium stress-strain isotherms of chitosan did not obey Mooney-Rivlin equation because of sharp increases in stress with extension ratio at high extensions. This is attributed mainly to interchain hydrogen-bonded interactions, but a possible contribution due to strain-induced crystallization cannot be ruled out. © 1997 John Wiley & Sons, Inc.
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    Lamellar thickening of polyethylene under high pressure (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 535-543 
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    ISSN: 0887-6266
    Keywords: polyethylene ; pressure ; phase ; melting ; ECC ; lamella ; DTA ; X-ray ; SAXS ; long period ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Single crystal mat (SCM) samples of polyethylene (PE) were prepared from dilute solution of p-xylen, then they were annealed at pressures of 200 and 500 MPa. Lamellar thickness of the original and annealed SCM samples was measured by small-angle X-ray scattering method. Orientation of the molecular chain in those SCM samples was investigated by wide-angle X-ray diffraction pattern. From these X-ray measurements, annealing temperature dependence of the lamellar thickness, i.e., lamellar thickening, under high pressure was obtained. Melting process of the SCM samples was also investigated at 200 and 500 MPa by high pressure differential thermal analysis. Then correspondence between the lamellar thickening and the melting process was studied. The lamellar thickness increases markedly with approaching to the melting temperature of the orthorhombic crystal even in the high pressure region where the high pressure phase (hexagonal phase) appears. The annealing temperature dependence curve of the lamellar thickness at 200 MPa can be superimposed on the curve at 500 MPa by shifting the curve along the temperature scale by 47 K. Large scale lamellar thickening occurs in the orthorhombic crystal phase in the high pressure region. The formation process of extended-chain crystal is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 535-543, 1997
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    Synthesis, characterization, and thermal and dielectric properties of three different methacrylate polymers with zwitterionic pendant groups (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 479-488 
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    ISSN: 0887-6266
    Keywords: polyzwitterions, synthesis of ; dielectric properties ; thermal properties on poly(zwitterions) ; morphology of polyzwitterions ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, characterization, thermal, and dielectric properties of three different zwitterionic methacrylates of the sulfobetaine type are presented. Diethylamine-ethyl-, 2-(diethylaminoethoxy)-ethyl-, and 2-(2-diethylaminoethoxy) ethoxy-ethyl-methacrylates were made to react with butanosultone to prepare monomers with variable flexibility. The flexibility of the lateral chain of the polymethacrylates decreased the glass transition temperature (Tg down to 300 K) of the polymers. A linear relationship between Tg and the number of carbon atoms was shown for these materials. X-ray diffraction and DSC experiments showed the formation of new ordered phases in these polymers, which inhibited their dipole conductivity. On heating, these phases were destroyed and values of conductivity of 10-7-10-3 S cm-1 were obtained in the studied range of temperature. Variation of conductivity with temperature was established according to the Arrhenius equation. Dielectric properties exhibited a small deviation of the Debye type behavior, and β parameters of the Cole-Cole equations were calculated for the synthesized polymers. © 1997 John Wiley & Sons, Inc.
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    Relaxation behavior of aliphatic-aromatic poly(ether amide)s as revealed by dynamic mechanical and dielectric methods (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 457-468 
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    ISSN: 0887-6266
    Keywords: poly(ether amide)s ; mechanical relaxation ; dielectric relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical and dielectric relaxation of a set of aromatic-aliphatic polyamides containing ether linkages have been examined as a function of temperature (-140 to 190°C) and frequency (3 to 106 Hz). The polymers differ in the orientation (meta and para) of the aromatic rings, in the length of the aliphatic chain, and in the number of ether linkages per repeating unit. Dynamic mechanical experiments showed three main relaxation peaks related to the glass transition temperature of the polymers (α relaxation), the subglass relaxations associated to the absorbed water molecules (β) and to the motion of the aliphatic moieties (γ). Dielectric experiments showed two subglass relaxation processes (β and γ) that correlates with the mechanical β and γ relaxations, and a conduction process (σ) above 50°C that masks the relaxation associated to the glass transition. A molecular interpretation is attempted to explain the position and intensity of the relaxation, studying the influence of the proportion of para- or meta- oriented phenylene rings, the presence of ether linkages and the length of the aliphatic chain. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 457-468, 1997
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    Wear and friction in glassy polymers: Microscratch on blends of polystyrene and poly (2,6-dimethyl-1,4-phenylene oxide) (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1295-1309 
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    ISSN: 0887-6266
    Keywords: polymer wear ; polymer friction ; scratch ; microscratch ; adhesion theory ; polymer fracture ; crazing ; shear yielding ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microscopic process of abrasive wear and friction in glassy polymers was studied by using a special microscratch technique. A miscible blend of polystyrene (PS) and poly(phenylene oxide) (PPO) was used. It was found that as the composition varies there seems to exist two wear regimes in the blends controlled by different breakdown mechanisms corresponding to the brittle - ductile transition. Detailed study of the contact loads and SEM micrographs indicate that abrasive wear in the glassy polymers is controlled by microcracking under the asperity contacts. The critical load τc for initiating microscopic cracks can be linked to the macroscopic wear via a statistical Weibull model where τc is taken to be the mean of a strength distribution function. On the other hand, the friction coefficient was found to be independent of the composition but to vary strongly with the contact load. It approaches zero at the extrapolated zero load, but increases rapidly and eventually levels off with contact load. This behavior can be understood by a simple frictional adhesion model in which the polymer deformation during a frictional contact is analyzed by considering the compressive plastic ploughing and shearing yielding around the asperity contact. The shear strength So of the polymer/asperity contacts was found to vary with the normal load. The vertical scratch hardness Hv, which characterizes the spontaneous indentation yielding on the polymer surface, was found to be independent of scratch length and depth, and indeed can be regarded as a material constant. Although both So and Hv can accurately describe the frictional behavior of the glassy polymers, they bear no correlation to abrasive wear in the same materials. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1295-1309, 1997
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    Infrared dichroism and polymer orientation in attenuated total reflection. Theoretical considerations (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1361-1372 
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    ISSN: 0887-6266
    Keywords: polymer ; infrared ; attenuated total reflection (ATR) ; dichroism ; molecular orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The orientation of molecular chains in polymers cannot be easily extracted from ATR spectra measurements. One can infer the orientation parameters by using plausible models that describe the type of the statistical distribution of the molecular chains in the sample. In this work, we are interested in the case of weakly aligned polymers. Therefore, we first adjusted the partial axial orientation model usually applied for strongly oriented polymers to the samples under our investigations and second, related the parameters describing the orientation configuration to the dichroic ratios in four particular molecular chain distributions: randomly, totally, partially, and elliptically oriented. A new method that leads to the determination of these dichroic ratios from ATR spectra is presented. This method is based only on the use of three distinct polarizations of the beam. Thus, all the practical difficulties usually encountered in the other methods are eliminated. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1361-1372, 1997
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    Hydrogen bonds in silk fibroin-poly(acrylonitrile-co-methyl acrylate) blends: FT-IR study (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1405-1414 
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    ISSN: 0887-6266
    Keywords: silk fibroin ; FT-IR spectroscopy ; hydrogen bonds ; polyacrylonitrile ; poly(acrylonitrile-co-methyl acrylate) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: FT-IR spectroscopy was used to study the specific interactions in polyacrylonitrile-silk fibroin (PAN-SF) and poly(acrylonitrile-co-methyl acrylate)-silk fibroin (PANMA-SF) blends. No specific interaction was found in PAN-SF blends. In PANMA-SF blends, however, a new 1703 cm-1 band, assigned to be hydrogen-bonded carbonyl groups of PANMA, appears, and its intensity depends on the compositions of the blends and the MA contents in PANMA. Furthermore, when the sample was heated, considerable changes in position and intensities of the hydrogen-bonded bands, in both stretching regions of the carbonyl group of PANMA and the hydroxl group of SF, were found, and these changes were irreversible on cooling. Finally, we suggested that the bands of hydrogen bonds in PANMA-SF blends may be the average result of several kinds of possible hydrogen bondings. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1405-1414, 1997
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    Epitaxial recrystallization of HDPE-quenched ultrathin films on oriented iPP substrates (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1415-1421 
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    ISSN: 0887-6266
    Keywords: epitaxy ; recrystallization ; high-density polyethylene ; isotactic polypropylene ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The recrystallization behavior of high-density polyethylene (HDPE) on the highly oriented isotactic polypropylene (iPP) substrates at temperatures below the melting temperature of HDPE has been investigated by means of transmission electron microscopy. The results obtained by the bright-field observation and the electron diffraction show that upon annealing the HDPE-quenched films on the oriented iPP substrates at temperatures below 125°C, only a small amount of HDPE recrystallizes on the iPP substrate with [001]HDPE//[001]iPP, while annealing the HDPE-quenched films at temperatures above 125°C, all of the HDPE crystallites recrystallize epitaxially on the iPP substrate with [001]HDPE//[101]iPP. © 1997 John Wiley & Sons, Inc. J Polym Sci B: 35: 1415-1421, 1997
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    Moisture sorption mechanism of aromatic polyamide fibers. V: Growth of crystallites in as-spun wet poly(p-phenylene terephthalamide) fiber during dehydration (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1423-1432 
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    ISSN: 0887-6266
    Keywords: crystallite ; Kevlar ; moisture sorption ; poly(p-phenylene terephthalamide) ; wide-angle x-ray diffraction ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Wide-angle x-ray diffraction studies were performed for as-spun wet poly(p-phenylene terephthalamide) fiber. The effects of sorbed water on the equatorial diffractions from the (110) and (200) crystal planes and on the meridional diffractions from the (002), (004), and (006) crystal planes were analyzed during desorption and absorption. There was no significant change in the d-spacing from the respective crystal plane irrespective of the moisture (water) regain. The ratio of the diffracted intensity from the (110) diffraction to that from the (200) diffraction remarkably increased by removing the sorbed water. The crystallite size estimated from the (110) diffraction, L110, also increased as the moisture regain decreased, while the L200 did not increase. The longitudinal size of paracrystallite, D001, also remarkably increased with the decrease in moisture regain with the lattice distortion factor, gII, kept unchanged. These results strongly suggested the growth of the crystallite via hydrogen bonds in the lateral (b-axis) direction. The growth of the lateral size of crystallite also accompanied the longitudinal growth of crystallite during desorption. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1423-1432, 1997
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    Dynamic mechanical investigations on drawn samples of isotactic polypropylene/EPM-Rubber blend (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1439-1448 
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    ISSN: 0887-6266
    Keywords: oriented PP/EPM films ; DMTA ; relaxations ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The physical behavior of isotropic and oriented samples of an isotactic polypropylene (iPP)/ethylene-propylene-copolymer (EPM) reactor blend was studied by performance of dynamic mechanical measurements over a wide temperature range (DMTA). The influence of thermal history and drawing procedure was examined. The results showed that with increasing draw ratio the uniaxial elastic modulus of the material was considerably enhanced, whereas the intensity and strength of the amorphous relaxations of both components were reduced. At a certain draw ratio, the glass transtions of iPP and EPM phenomenologically merged and appeared as a single relaxation. The crystalline relaxation of iPP emerged with increased draw ratio at higher temperatures and was better seperated and easier to detect. The effects observed were attributed to the orientation of the crystallites in a fibrillar structure and to the restricted molecular mobility in amorphous regions. Measurements by differential scanning calorimetry (DSC) and x-ray diffraction of several drawn samples were performed to determine the effects of drawing on the melting behavior and the crystal orientation in the semicrystalline polymer. For comparison, some results of analogous studies on neat isotactic PP are presented and discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1439-1448, 1997
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    Adhesion of silicon oxide layers on poly(ethylene terephthalate). I: Effect of substrate properties on coating's fragmentation process (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1449-1461 
    Details
    ISSN: 0887-6266
    Keywords: adhesion ; oxide coating ; fragmentation test ; molecular orientation ; substrate temperature ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fragmentation tests in the uniaxial mode were performed on poly(ethylene terephthalate) (PET) films coated with a 100 nm thin silicon oxide layer. The coating's fragmentation process was analyzed in light of the mechanical behavior of the polymer substrate. It was shown that, upon unloading samples strained to less than 4% nominal strain, strain recovery leads to the closure of coating cracks. The usual fragmentation diagram, which shows the crack density (CD) versus applied strain, was used to identify the various energy dissipation mechanisms controlling the fragmentation process. An alternative presentation of CD versus true stress provided accurate measurements of both fragmentation and saturation onsets. The interfacial strength was modeled from the CD at saturation according to the Kelly-Tyson approach, including a Weibull distribution of the coating strength. The prediction was compared to the substrate shear stress at saturation. Effects of substrate yield, temperature, and molecular orientation are discussed. It was shown that the coating deposition by evaporation on the PET substrate did not induce structural changes at the polymer interface, whereas heat treatments increased the polymer crystallinity in the interfacial zone, resulting in higher interfacial strength. © 1997 John Wiley & Sons, Inc. J. Polym Sci B: Polym Phys 35: 1449-1461, 1997
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    A generalized model for the yield behavior of epoxy networks in multiaxial stress states (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1611-1619 
    Details
    ISSN: 0887-6266
    Keywords: epoxy ; yield criterion ; molecular weight between crosslinks ; von Mises ; failure envelope ; strain rate ; thermal activation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several yield criteria for glassy polymers are reviewed, and their limitations in predicting the effects of stress state, strain rate, test temperature, and molecular architecture are noted. These criteria are then generalized, so that a working model can be developed for predicting the yield response of glassy networks subjected to a multiaxial state of stress. To form the model, we summarize the phenomenological yield and fracture response of amine cured epoxies. In stress states ranging from uniaxial compression to biaxial tension, the yield response of these glassy networks follows a modified von Mises criterion (τyoct = τyooct - μσm), when tested at a constant temperature and octahedral shear strain rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $end\{document}oct. Furthermore, changes in \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $end\{document}oct and molecular weight between crosslinks, Mc, affect τyooct only, and μ remains unchanged. This was shown to be true for a broad range of Mc (380 to 1790 g/mol). Additional results are included to illustrate the effects of temperature and strain rate on yield response. These results show that the yield behavior of epoxy resins is best described by a thermally activated process, similar to an Eyring type process. Finally, we extend the model to include intrinsic properties of the resin (e.g., Mc, φ, and Tg) and compare the model's predictions with experimental results. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1611-1619, 1997
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    Solid-state relaxations in linear low-density (1-octene comonomer), low-density, and high-density polyethylene blends (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1633-1642 
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    ISSN: 0887-6266
    Keywords: 1-octene based linear low-density polyethylene (LLDPE) ; low-density polyethylene (LDPE) ; high-density polyethylene (HDPE) ; molecular relaxations in solid state ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Extensive thermal and relaxational behavior in the blends of linear low-density polyethylene (LLDPE) (1-octene comonomer) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated to elucidate miscibility and molecular relaxations in the crystalline and amorphous phases by using a differential scanning calorimeter (DSC) and a dynamic mechanical thermal analyzer (DMTA). In the LLDPE/LDPE blends, two distinct endotherms during melting and crystallization by DSC were observed supporting the belief that LLDPE and LDPE exclude one another during crystallization. However, the dynamic mechanical β and γ relaxations of the blends indicate that the two constituents are miscible in the amorphous phase, while LLDPE dominates α relaxation. In the LLDPE/HDPE system, there was a single composition-dependent peak during melting and crystallization, and the heat of fusion varied linearly with composition supporting the incorporation of HDPE into the LLDPE crystals. The dynamic mechanical α, β, and γ relaxations of the blends display an intermediate behavior that indicates miscibility in both the crystalline and amorphous phases. In the LDPE/HDPE blend, the melting or crystallization peaks of LDPE were strongly influenced by HDPE. The behavior of the α relaxation was dominated by HDPE, while those of β and γ relaxations were intermediate of the constituents, which were similar to those of the LLDPE/HDPE blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1633-1642, 1997
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    Thermodynamic interactions in rubbery polymer/gas systems (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1049-1053 
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    ISSN: 0887-6266
    Keywords: thermodynamic interaction ; Flory-Huggins parameter ; rubbery polymer ; gas ; Henry's law coefficient ; partial molar volume ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Flory-Huggins interaction parameters χ for 23 gases (He, Ne, Ar, Kr, Xe, H2, N2, O2, N2O, CO2, CH4, C2H4, C2H6, C3H6, C3H8, 1,3-C4H6, four C4H8's, n-C4H10, iso-C4H10, and n-C5H12) in five rubbery polymers (1,2-polybutadiene (PB), poly(ethylene-co-vinyl acetate)) (EVAc), polyethylene (PE), polypropylene (PP), and poly(dimethyl siloxane) (PDMS) were determined from either literature data on Henry's law coefficient and partial molar volume or those on sorptive dilation for each polymer/gas system. Values of χ for the gases increased in the order of PDMS 〈 PP ≡ PB 〈 EVAc ≡ PE. Among the gases except He and H2 whose χ values are not reliable, Ne and Xe have respectively the highest and the lowest values of χ for the polyolefins. The χ values of the hydrocarbons were compared together with previously reported χ values of n-alkanes C3-C10. The dependencies of χ upon concentration and temperature were discussed on the basis of the literature data. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1049-1053, 1997
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    Interpretation of the nonisothermal crystallization kinetics of polypropylene using a power law nucleation rate function (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1077-1093 
    Details
    ISSN: 0887-6266
    Keywords: nucleation ; crystallization kinetics ; polypropylene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A nucleation rate function is proposed for use in analyzing the overall crystallization kinetics of polymers. This function allows for the possibility that the nucleation rate varies substantially during the crystallization. This feature is particularly useful in analyzing nonisothermal crystallization, but it can be used to analyze isothermal crystallization as well. The nucleation rate function was used in the derivation of a modified transformation kinetics equation of the Avrami type. The modified Avrami equation was found to be suitable for kinetics analysis for the data obtained from nonisothermal crystallization at rapid cooling rates. Kinetics parameters used to describe nonisothermal crystallization under rapid cooling rates are presented and discussed. These include crystallization induction time, plateau (crystallization) temperature, crystallization half-time, crystallization rate constant, Avrami index, and newly defined quantities called nucleation index, geometric index, and nucleation rate constant. The procedure used to obtain the nucleation rate constant and nucleation index for the nucleation rate function is described and illustrated by application to the analysis of the crystallization kinetics of polypropylene. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1077-1093, 1997
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    Transmission electron microscopy of 3F/PMDA-polypropylene oxide triblock copolymer based nanofoams (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1067-1076 
    Details
    ISSN: 0887-6266
    Keywords: transmission electron microscopy ; block copolymer ; polyimide ; nanofoam ; porous films ; polymer foam ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transmission electron microscopy was performed on a polymeric nanofoam material, derived from a triblock copolymer composed of a fluorinated polyimide center block, 3F/PMDA (derived from pyromelletic dianhydride (PMDA) and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F)) and polypropylene oxide (PO) end blocks. The cast and imidized polymer exhibits a microphase-separated morphology consisting of PO microdomains within a polyimide matrix. The final nanofoam material is obtained by decomposing PO microdomains into low molecular weight products, which diffuse out of the polyimide matrix leaving nanometer length scale voids. Ruthenium tetroxide staining prior to microscopy was used to enhance the contrast between the 3F/PMDA matrix and the PO microdomains or voids, which permitted a more detailed view of the microstructure of both the foamed and unfoamed materials. From the power spectra of the micrographs, spatial correlation between the PO microdomains in the unfoamed material and between the voids in the foam were found. An interdomain separation distance of ca. 37 nm was observed. Analysis of the image yielded an average area of 411 nm2 for the PO domains. The analysis indicated that the PO domains were oblong, having average major and minor dimensions of 35 and 12.5 nm, respectively. An autocorrelation of the image showed that the domain center of masses were positioned 41 nm apart, in close agreement with the domain spacing (ca. 37 nm) found as described above. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1067-1076, 1997
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    The influence of stereoregularity on the miscibility of poly(propylene)s (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1135-1144 
    Details
    ISSN: 0887-6266
    Keywords: blends ; poly(propylene)s ; phase behavior ; stereoregularity ; solubility parameters ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melt miscibility of atactic poly(propylene) (a-PP) with isotactic (i-PP) and syndiotactic poly(propylene) (s-PP), respectively, is investigated by diffusion experiments of i-PP/a-PP/i-PP or s-PP/a-PP/s-PP sandwich specimens using polarized light microscopy. It is shown that the system a-PP/i-PP is miscible in the melt, whereas for the system a-PP/s-PP no evidence for melt mixing is found. Pressure-volume-temperature (PVT) measurements of the three poly(propylene)s are carried out in order to determine the characteristic parameters of the Flory-Orwoll-Vrij equation-of-state theory. Theoretical predictions using the solubility parameter concept are in agreement with the observed miscibility behavior of the blends. Differences in the cohesive energy densities of a-PP and i-PP on the one side, and s-PP on the other side, are found to be responsible for the phase behavior of the mixtures of poly(propylene)s with different stereoregularity. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1135-1144, 1997
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    Effect of the directionality of the ester group on the formation of hairpins in polyesters containing naphthalene and a flexible spacer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1127-1133 
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    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; molecular dynamics ; naphthalene ; polyester ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady-state fluorescence measurements and molecular dynamics simulations have been used to study the intramolecular formation of excimers in five model compounds for polyesters containing naphthalene groups separated by flexible spacers. The model compounds are derived from 2-hydroxynaphthalene and HOOC—(CH2)n—COOH, n = 2-6. The ratio of the intensity of excimer and monomer emissions, ID/IM, is nearly independent of the viscosity of the medium, η, over the range covered in dilute solution. Although ID/IM is always very small, it shows an odd-even effect for the first four members of the series, with maxima when n is odd. Molecular dynamics simulations provide an explanation for the small values of ID/IM, their weak dependence on η, and the trend of ID/IM with n. The results for the present series of model compounds are compared with previous work, which reported larger values of ID/IM, and a stronger dependence of ID/IM on η, for bichromophoric compounds derived from 2-naphthoic acid and aliphatic glycols, where the direction of the ester groups is reversed. The origin of the difference in the behavior of ID/IM in the two series is identified. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1127-1133, 1997
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    Distribution of chain lengths and composition in terpolymers (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1161-1166 
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    ISSN: 0887-6266
    Keywords: random terpolymers ; chain composition ; instantaneous distribution ; statistical heterogeneity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The instantaneous distribution of chain composition for random terpolymers has been derived by adopting a similar strategy to that used by Stockmayer. The analytical result shows the same Gaussian behavior for the random terpolymer distribution. When the concentration of the third comonomer is low and they are almost individually dispersed along the chain (the quasiterpolymer case), the explicit distribution is given by (the Stockmayer's copolymer result)*(ωt)t, where t and ω are the concentration and the relative probability of incorporating the third comonomer within a chain. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1161-1166, 1997
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    Dynamic scattering properties of mixtures of cyclic and linear homopolymers and copolymers (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1191-1200 
    Details
    ISSN: 0887-6266
    Keywords: cyclic chains ; linear chains ; copolymers ; homopolymers ; relaxation frequency ; dynamic scattering ; interaction parameter ; random phase approximation (RPA) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic scattering properties of mixtures of cyclic copolymers and homopolymers are discussed. These properties are compared with those characterizing linear chain mixtures in similar conditions. The differences between cyclic and linear chains are introduced through the form factors only. The interaction parameter between different monomer species are assumed to be the same whether they belong to cyclic or linear chains. The dynamical model is based upon a generalization of the random phase approximation neglecting hydrodynamic interaction and mode coupling effects. Despite these simplifications, substantial differences are found in the dynamics of mixtures containing cyclic copolymers and homopolymers when compared to those of linear chain systems in similar conditions of temperature, concentration, and molecular weight. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1191-1200, 1997
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    Platinum nanocatalysts immobilized on latex supports (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1207-1216 
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    ISSN: 0887-6266
    Keywords: latexes ; platinum nanoparticles ; catalytic activities ; protective polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several latex dispersions of different hydrophobicity were investigated with respect to their ability to adsorb platinum nanoparticles that had been reduced in their presence. Two reduction methods were tested, specifically the slower method of refluxing the alcoholic solutions and the more rapid method of reaction with KBH4. The immobilization of the metal particles and their nanosize dimensions were demonstrated by transmission electron microscopy, and their catalytic activity was tested by the hydrogenation of cyclohexene as a model reaction. Some additional immobilized platinum nanoparticles were prepared in the presence of various protective polymers. This can lead to various advantages with respect to, for instance, the stability and the catalytic properties of these materials. Even in the presence of such additional protective polymers, the platinum nanoparticles remained immobilized for some of the hydrophobic latexes both before and after catalytic hydrogenations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1207-1216, 1997
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    Continuity of solvent quality in polymer solutions. Poor-solvent to Θ-solvent continuity in some polystyrene solutions (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1251-1259 
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    ISSN: 0887-6266
    Keywords: demixing ; polystyrene ; phase equilibria ; solvent ; consolute temperatures ; pressure ; negative pressure ; methyl acetate ; ethyl formate ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Critical temperatures for polystyrene/methyl acetate (PS/MA) and polystyrene/ethyl formate (PS/EF) solutions were measured at positive (PS/MA, PS/EF) and negative (PS/MA) pressure. The results confirm that solvent quality is sensitive to pressure; some solvents, designated Θ, at Pnominal ∼ 0, undergo a Θ-to-poor transition at negative pressure, and others, nominally designated “poor,” show a poor-to-Θ transition at positive pressure. Thus, any dichotomous division into sets of “poor” and “Θ” solvents is inaccurate, unless it accounts for the effects of pressure and other variables on solvent quality. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1251-1259, 1997
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    Poly(4-methylpentene-1)/hydrogenated oligo (cyclopentadiene) blends: Miscibility, tensile stress-strain, and dynamic mechanical behaviors (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1269-1277 
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    ISSN: 0887-6266
    Keywords: poly(4-methylpentene-1) ; hydrogenated oligo (cyclopentadiene) ; blends ; miscibility ; mechanical properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article discusses the influence of the oligomeric resin, hydrogenated oligo(cyclopentadiene) (HOCP), on the morphology, and thermal and tensile mechanical properties of its blends with isotactic poly(4-methylpentene-1) (P4MP1). The P4MP1 and HOCP are found not miscible in the melt state. P4MP1/HOCP blends after solidification contain three phases: the crystalline phase of P4MP1, an amorphous phase of P4MP1, and an amorphous phase of HOCP. From optical micrographs obtained at 150°C, it is found that the solidified blends show a morphology constituted by P4MP1 microspherulites and small HOCP domains homogeneously distributed in intraspherulitic regions. DSC and DMTA results show that the blends present two glass transition temperatures (Tg) equal to the Tgs of the pure components. The tensile mechanical properties have been investigated at 20, 60, and 120°C. At 20°C both the HOCP oligomer and the amorphous P4MP1 are glassy, and it is found that all the blends are brittle and the stress-strain curves have equal trends. At 60°C the HOCP oligomer is glassy, whereas the amorphous P4MP1 is rubbery. The tensile mechanical properties at 60°C are found to depend on blend composition. It is found that the Young's modulus, the stresses at yielding and break points slightly decrease with HOCP content in the blends and these results are related to the decrease of blend crystallinity. The decrease of the elongation at break is accounted for by the presence of glassy HOCP domains that act as defects in the P4MP1 matrix, hampering the drawing. At 120°C both the amorphous phases are rubbery. It is found decreases of Young's modulus, stresses at yielding and break points. These results have been related to the decrease of blend crystallinity and to the increase of the total rubbery amorphous phase. Moreover, it is found that the blends present elongations at break equal to that of pure P4MP1. This constancy is attributed to: (a) at 120°C the HOCP domains are rubbery and their presence seems not to disturb the drawing of the samples; (b) a sufficient number of the tie-molecules and entanglements of P4MP1 present in the blends. In fact, although the numbers of tie-molecules and entanglements decrease in the blends, increasing the HOCP oligomer, they seem to be enough to keep the material interlaced and avoid earlier rupture. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1269-1277, 1997
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    Densely crosslinked polycarbosiloxanes. II: Thermal and mechanical properties (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1311-1331 
    Details
    ISSN: 0887-6266
    Keywords: branched prepolymers ; hydrosilylation cure ; densely crosslinked polymers ; thermal and mechanical properties ; tough-brittle transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal and mechanical properties of two densely crosslinked polycarbosiloxane systems were investigated in relation to the molecular structure. The networks were prepared from functional branched prepolymers and crosslinked via a hydrosilylation curing reaction. The prepolymers having only vinyl functionalities (poly[phenylmethylvinyl]siloxanes) were crosslinked by using crosslinking agents with reactive silicon-hydrogen groups. In prepolymers having both silicon-vinyl and silicon-hydrogen groups (poly[phenylmethylvinylhydro)]siloxanes crosslinking took place intermolecularly. The thermal and mechanical properties of the polymer networks were found to be dependent on the phenyl —Si—O3/2 (branches) content in the prepolymer, the number of elastically effective crosslinks, the elastically effective network chain density and molecular weight between crosslinks, length of the chain segments introduced by the hydrosilylation crosslinking reaction, and the number of dangling ends. As a consequence of the dense crosslinking, the mechanical properties were also strongly dependent on the glass transition temperature. A tough-brittle transition was observed around the glass transition temperature of the polymer networks. The properties of the poly(phenylmethylvinylhydro)siloxane networks were found to be superior to those of the poly(phenylmethylvinyl)siloxane networks. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1311-1331, 1997
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    Adsorption as a mechanism for nucleating activity: A thermodynamic explanation (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1333-1338 
    Details
    ISSN: 0887-6266
    Keywords: polymer ; adsorption ; crystal nucleation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Although polymeric crystallization processes heterogeneously induced by foreign surfaces have been the subject of an overwhelming amount of experimental investigations over the last 30 years, this topic suffers from the absence of theoretical or predictive tools describing the polymer-substrate interactions at work in surface-induced nucleation phenomena. In this work we consider the case when polymer chains are attracted to a flat surface (adsorption). Using a single-chain approach, we propose a model for deriving the thermodynamic potential barrier to nucleation within an adsorbed chain. It is shown that, because of the reduction of the configurational entropy of the entire chain prior to undercooling, forming a nucleus of a certain volume within the adsorbed chain costs less energy. In the case of weakly adsorbing surface, using the scaling treatment of de Gennes, we clearly relate the lowering of the thermodynamic potential for nucleation to the strength of the attractive interactions with the surface. This work points out adsorption as a possible mechanism for the nucleating activity of a surface. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1333-1338, 1997
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    Dispersive aspects of the high-field hopping mobility of molecularly doped solids with dipolar disorder (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2803-2809 
    Details
    ISSN: 0887-6266
    Keywords: dipolar disorder ; photoconductors ; organic conductors ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The time-of-flight mobility of photoinjected charges in molecularly doped polymers obeys a Poole-Frenkel law, μ ∝ exp(\documentclass{article}\pagestyle{empty}\begin{document}$\gamma \sqrt E $\end{document}), which is commonly viewed as arising from hopping transport among sites with a large degree of energetic disorder. Recent theoretical investigations have focused on long-range correlations that characterize site energies when the dominant mechanism for energetic fluctuations is the interaction of charge carriers with randomly-oriented permanent dipoles of the dopant and host polymer. An exact calculation of the steady-state drift velocity vd for a one-dimensional system with correlated dipolar disorder predicts a Poole-Frenkel law similar to that observed. In order to investigate another feature commonly observed in the high-field measurements, namely, the anomalous dispersion of the current-time transients, we have performed an exact calculation of the field-dependent diffusion constant D for the same dipolar disorder model. In the bulk limit we obtain an expression D = (KT/e) ∂vd/∂E that generalizes the normal Einstein relation and predicts a strongly field-dependent diffusion constant. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2803-2809, 1997
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    Morphology of anisotropic polymer-dispersed liquid crystals and the effect of monomer functionality (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2825-2833 
    Details
    ISSN: 0887-6266
    Keywords: holographic gratings ; morphology ; functionality ; liquid-gel demixing ; network ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphology of transmission gratings with varying Bragg spacings formed using polymer-dispersed liquid crystals were examined using high-resolution scanning electron microscopy and image analysis techniques. The effect on the morphology of small changes in the overall functionality of the prepolymer syrup was observed. An increase in the amount of monofunctional compound resulted in small, nearly spherical domains (〈100 nm in diameter) confined in well-defined lamellae for samples with a 0.49 μm Bragg spacing. A decrease in concentration (an effective increase in monomer functionality) at this Bragg spacing resulted in larger domains (100-200 nm) with much greater distribution of sizes and shapes. The local volume fractions of discrete liquid crystalline (LC) domains was considerably larger in the latter case. An increase in the Bragg spacing to 1.35 μm also resulted in well-defined lamellae of LC domains, although much more coalescence into irregularly shaped individual domains was observed. Surprisingly, the local volume fraction of LC increased in the larger Bragg spacing samples. The morphology results are discussed qualitatively in terms of liquid-gel demixing where the inherent crosslink density and elasticity of the polymeric host must be considered in phase separation processes on the nanoscale. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2825-2833, 1997
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    Can random copolymers serve as effective polymeric compatibilizers? (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2835-2842 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; random copolymer ; compatibilizer ; encapsulation ; coalescence ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We investigate the compatibilizing performance of a random copolymer in the melt state, using transmission electron microscopy. Blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) are chosen as a model system, and a random copolymer of styrene and methyl methacrylate (SMMA) with 70 wt % styrene is used as a compatibilizer. From TEM photographs it is clear that SMMA moves to the interface between PS and PMMA domains during melt mixing, and forms encapsulating layers. However, the characteristic size of the dispersed phase increases gradually with annealing time for all blend systems studied. This demonstrates that the encapsulating layer of SMMA does not provide stability against static coalescence, which calls into question the effectiveness of random copolymers as practical compatibilizers. We interpret the encapsulation by random copolymers in terms of a simple model for ternary polymer blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2835-2842, 1997
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    A process-structure-property study of anisotropic PMDA-ODA films (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 777-788 
    Details
    ISSN: 0887-6266
    Keywords: PMDA-ODA polyimide ; intrinsic molecular properties ; sheet mapping ; fabrication processes ; three-dimensional orientation functions ; anisotropic coefficient of thermal expansion (CTE) ; anisotropic mechanical moduli ; anisotropic compliances ; anisotropic dielectric constants ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A practical methodology for the correlation and prediction of the process-property performance of advanced materials is developed. The model polymer studied is PMDA-ODA polyimide. The connecting link between the process and the properties is the structural state of the polymer. An essential ingredient for a quantitative characterization of the system is a knowledge of its phase state and intrinsic molecular properties. The intrinsic molecular properties define the limiting performance properties available to the polymer. Anisotropic films and sheets produced by five different fabrication processes are examined. Maps of the molecular symmetry axis, the orientation function, and the thickness distributions of two 50-in.-wide sheets fabricated differently are measured nondestructively for process comparison. Four other film fabrication processes are examined and their three-dimensional orientation states determined and correlated. A three-dimensional orientation function triangular plot permits simultaneous representation of the different fabrication processes on the same figure and allows the investigator to choose the most economic and efficient fabrication route. The structure-property study includes the structural correlation and intrinsic molecular property determination of the anisotropic coefficient of thermal expansion (CTE), the anisotropic mechanical moduli and compliances, and the anisotropic dielectric constants. 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 777-788, 1997
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    Moisture effects on the glass transition and the low temperature relaxations in semiaromatic polyamides (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 807-815 
    Details
    ISSN: 0887-6266
    Keywords: moisture effect ; glass transition ; low temperature relaxations ; semiaromatic amorphous polyamides ; hydrogen bonding ; molecular analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of moisture absorption on the primary (glass) transition (Ta or Tg) and the low temperature relaxations of semiaromatic amorphous polyamides synthesized by isomeric aliphatic diamine and metha or para oriented phthalicdiacids has been investigated by means of differential scanning calorimeter (DSC) and dynamic mechanical thermal analyser (DMTA). The glass transition of semiaromatic polyamides was lowered due to the water absorption, and the β and the γ relaxations were as well. From the observed Tg and the difference in the heat capacity, the calculated Tg depression per 1 wt % water content was 12.3 K and the result was in good agreement with the experimental data. The depression of the glass transition may be expressed by the same manner as the plasticization of nylon 6 by water. The depressed β relaxation observed in the specimen containing a few percent of moisture was splitted into two transitions due to the reduction of water content, of which one was the elevation of the Tβ and another was the simultaneous appearance of the Tγ, and then the single Tγ solely was observed for the completely dried specimen. The Tγ seemed to be merged into or not to be observed by the large and broad Tβ transition when the sample was governed by a few percent of water, then it was emerged from the Tβ due to water desorption. Thus, the Tβ is believed to arise from the intermolecular hydrogen bonding between water molecules or between water and amide groups in wet polyamides. In addition, the γ relaxation originated from the peptide groups is attributable to the inter- and intramolecular hydrogen bonding between amide groups. © 1997 John Wiley & Sons, Inc. J Polyn Sci B: Polym Phys 35: 807-815, 1997
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    Conformation of amphiphilic branch chain in copolymer surfactants on interface (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 827-830 
    Details
    ISSN: 0887-6266
    Keywords: conformation ; copolymer surfactant ; amphiphilic branch chain ; oxyethylene segment ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The conformation of amphiphilic branch chain in a new type of copolymer surfactants on interface was studied. The results of laser light scattering demonstrated that the branch chain can only lie on the air/water interface. By means of XPS measurement with variable angles, the molecular conformations in different thickness of the copolymer layer were obtained. Depending on the chemical nature of the copolymer surfactants, the oxyethylene segments of the branch chains will have loop-train, train, or loop molecule conformations on the surface. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 827-830, 1997
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    A TSC investigation of polymer-polymer contact charging (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2901-2912 
    Details
    ISSN: 0887-6266
    Keywords: polymer ; contact charging ; TSC ; interface ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The transfer of charge across the interface between two materials brought into contact was studied by measuring the small currents produced when layered films composed of two dissimilar films were first heated and then held under isothermal conditions. It was found that, given a fixed electrode orientation, the polarity of the current generally reversed when the relative position of the films were reversed. The sense of the current was in agreement with that expected from the polymer work functions. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2901-2912, 1997
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    The reaction of furfuryl alcohol resins with hexamethylenetetramine: A 13C and 15N high-resolution solid-state NMR study (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2233-2243 
    Details
    ISSN: 0887-6266
    Keywords: furfuryl alcohol resins ; crosslinking reactions ; hexamethylenetetramine ; high-resolution solid-state NMR ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactions between furfuryl alcohol (FA)/poly(furfuryl alcohol) (PFA) and hexamethylenetetramine (HMTA) have been studied by 13C and 15N high-resolution solid-state NMR techniques. Highly crosslinked polymer networks similar to those obtained from the thermal curing of FA resins under acidic condition are formed. Possible reaction pathways are postulated on the basis of changes of chemical structures during the curing; α-substituted furfurylamines are shown to be the initial intermediates. Their further reactions with FA/PFA, together with thermal decomposition, produce methylene linkages between furan rings, resulting in chain extension and crosslinking, which occurs at both the methylene linkages and the 3- or 4-C of furan rings. Various side-products such as amines, imines, amides, imides, and nitriles are also formed during the reactions, and some of these can remain in the resins up to 205°C. The crosslinked network can be heterogeneous with different structures on nanometer scales when higher oligomers of FA resins react with HMTA. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2233-2243, 1997
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    Effect of ultraviolet light irradiation on gas permeability in polyimide membranes. 1. Irradiation with low pressure mercury lamp on photosensitive and nonphotosensitive membranes (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2259-2269 
    Details
    ISSN: 0887-6266
    Keywords: polyimide membrane ; ultraviolet light irradiation ; crosslinking ; physical changes ; gas permeability ; sorption property ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two types of polyimide membranes; one crosslinkable and the other noncrosslinkable using ultraviolet light irradiation (UV irradiation), were prepared and investigated concerning the effect of UV irradiation on their gas permeabilities and selectivities. Permeability and diffusion coefficients for O2, N2, H2, and CO2 were determined using the vacuum pressure and time lag method. Sorption properties for carbon dioxide were carried out to evaluate the changes in the free volume in the membranes due to the irradiation. In both membranes, permeability coefficients for all gases used in this study decreased and permselectivity, particularly for H2 over N2, increased with increasing UV irradiation time without a significant decrease in the flux of H2. The coefficients depended on the membrane thickness, suggesting asymmetrical changes in both membranes due to UV irradiation. It was suggested by an attenuated total reflection (ATR) FTIR method and analysis of the gas sorption properties of the membranes that the physical changes due to UV irradiation at the irradiated side in both membranes significantly affected their gas permeation properties compared with the chemical changes, especially the crosslinking in the crosslinkable type. © 1997 John Wiley & Sons, Inc. J. Polym Sci B: Polym Phys 35: 2259-2269, 1997
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    Heat capacity and phonon dispersion in poly(L-methionine) (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2281-2292 
    Details
    ISSN: 0887-6266
    Keywords: conformation ; phonon dispersion ; α-helix ; normal modes ; poly(L-leucine) ; density of states ; heat capacity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(L-methionine) (PMet) is one of the two sulfur containing polyamino acids. Raman, FTIR spectra, and heat capacity measurements of PMet have been well interpreted through the normal mode analysis and the density of states derived therefrom. Earlier interpretation of heat capacity data is limited because it is based on the Tarasov model, wherein the concept of group frequency and skeletal similarity are used. A special feature of some dispersion curves is their tendency to bunch in the neighborhood of the helix angle. This has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2281-2292, 1997
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    Phase separation in segmented poly(urethane urea) copolymers during reaction injection molding (RIM) polymerization (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 865-873 
    Details
    ISSN: 0887-6266
    Keywords: poly(urethane urea) ; phase separation ; FTIR spectroscopy ; reaction injection molding ; domain size ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In situ experiments were performed with a portable RIM (reaction injection molding) minimachine interfaced to an FTIR spectrophotometer to follow the reaction chemistry and monitor phase separation of copoly(urethane urea)s during RIM polymerization. The PUU copolymers were based on ethylene oxide-capped poly(propylene oxide) polyether diol, 3,5-diethyltoluenediamine (DETDA), and uretonimine liquefied 4,4′-diphenylmethane diisocyanate. The effect of catalyst concentration on the degree of phase separation in the as-molded RIM PUU copolymers was investigated by using differential scanning calorimetery and scanning electron microscopy as supplementary methods. The results suggested that an increase of degree of phase separation and a decrease of the size of hard-segment-rich domains take place with a rise of catalyst concentration. The morphological feature was a consequence in combination with the increase in relative rate of urethane formation and the ordering of hydrogen bonding through urea groups. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 865-873, 1997.
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    Prediction and analysis of nonisothermal crystallization of polymers (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 875-888 
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    ISSN: 0887-6266
    Keywords: PEEK ; POM ; PET ; PP ; crystallization kinetics ; nonisothermal crystallization ; thermal analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization behavior of polyetheretherketone (PEEK), polyoxymethylene (POM), polyethyleneterephtalate (PET), and polypropylene (PP) under nonisothermal conditions has been studied. Differential scanning calorimetry was used to monitor crystallization from the melt and a kinetic model has been proposed to describe three-dimensional spherulitic crystal growth. The model, which accounts for crystalline growth rate, uses two modified Avrami equations to represent both heterogeneous and homogeneous nucleation and growth processes. The model parameters are all associated with physical constants. The predicted evolution of absolute crystallinity showed good agreement with experimentally obtained values for a wide range of cooling rates. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 875-888, 1997
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    Structure-properties relationship in spun fibers of poly(ethylene terephthalate): Comparisons between samples obtained by terephthalic acid or dimethyl terephthalate processes (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 889-896 
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    ISSN: 0887-6266
    Keywords: poly(ethylene terephtalate) ; terephthalic acid process ; dimethyl terephtalate process ; spun fibers ; structure-properties relationship ; orientation of amorphous phase ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some properties and structural aspects of fibers obtained by spinning, in a wide range of take-up speed (2,800-4,400 m/min), of commercial samples of PET, produced by dimethyl terephthalate (DMT) and the terephthalic acid (TPA) processes, are compared. For a same take-up speed, the considered fibers from TPA are spun at lower pack pressures and always show higher tenacity and lower ductility than fibers from DMT. X-ray diffraction, density, and birefringence measurements indicate that, for the fibers from the DMT process, an earlier crystallization occurs which prevents the progress of the orientation of the amorphous phase. The lower molecular orientation in the amorphous phase of the fibers from DMT, in turn, accounts for their lower tenacity. The earlier crystallization of the fibers from DMT would be related to their slightly higher melting temperatures and melt viscosities, which could be due to the lower amount of constitutional defects (diethylene glycol content) in the considered PET samples from DMT compared with those from TPA. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 889-896, 1997
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    Dielectric relaxation studies of aromatic polyamides (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 919-927 
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    ISSN: 0887-6266
    Keywords: dielectric relaxation ; aromatic polyamides ; rotational barrier ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric relaxation spectroscopy (DRS) is presented for a family of four aromatic polyamides trying to relate the structure of the lateral groups to the molecular mobility. A prominent sub-Tg absorption is always seen followed in some cases by remanent dielectric activity at room temperature and a subsequent increase of the loss permittivity. The low temperature relaxation is analyzed in terms of a Fuoss-Kirkwood equation to obtain the broadness and the strength of these relaxations as well as the activation energy (ranging from 10 to 11 Kcal/mol). The low frequency conductive peak shows in each case a half-width higher (1.30) than those corresponding to a single relaxation time peak (1.144). These values of the half-width are an indication of the complex character of these phenomena. A final discussion of the rotational barriers of the lateral chains rules out that such motions are the only molecular origin for the gamma relaxation. Instead, some kind of motion involving the main chain and where the interchain interactions play a significant role should be considered as responsible for that relaxation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 919-927, 1997
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    Physical aging of a polyetherimide: Volume recovery and its comparison to creep and enthalpy measurements (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 929-936 
    Details
    ISSN: 0887-6266
    Keywords: physical aging ; glass ; polyetherimide ; volume and enthalpy recovery ; creep ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Volume recovery measurements have been used to study the physical aging behavior of a polyetherimide. Isothermal aging temperatures near Tg were studied with aging times ranging up to several days. The volume decreases during physical aging and levels off at equilibrium. For comparison purposes, the data are normalized to yield the departure from equilibrium which varies from unity at very short aging times to zero when equilibrium is reached. As the aging temperature decreases, the normalized curves are shifted to longer times without a significant change in shape. Hence, the data can be reduced by aging time - temperature superposition. The temperature dependence of the shift factors used to reduce the volume recovery data and the times to reach equilibrium for the volume recovery follow the WLF equation and agree within experimental error with the values from enthalpy and creep measurements obtained in previous work. However, the approach to equilibrium for volume appears to differ from that of enthalpy, with volume recovery being faster than the enthalpy recovery at short times. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 929-936, 1997
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    Phase and orientational behaviors in liquid crystalline main-chain/side-group block copolymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 21-29 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystal ; block copolymer ; polyester block ; polymethacrylate block ; magnetic field ; X-ray diffraction ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase and orientational behaviors of a series of liquid crystalline (LC) AB-type diblock copolymers comprising thermotropic main-chain (MC) polyester and side-group (SG) polymethacrylate blocks were investigated by X-ray diffraction. The MC and SG blocks were phase separated and gave rise to their individual mesophases that coexisted at equilibrium. The samples were oriented by using either a magnetic field or a mechanical field. In magnetically aligned samples both the MC and SG microphases were oriented with their smectic planes orthogonal to the magnetic field direction, independent of the copolymer composition. Mechanically aligned, fiber samples showed different orientations of the MC and SG smectic planes for different sample compositions. In this case the disposition of the smectic planes of the MC and SG blocks was driven by the relative length of the two blocks. Some features of the X-ray patterns of the copolymers were compared to those of the MC and SG homopolymers. In addition, the MC smectic domains crystallized on annealing without affecting the orientation that had been achieved by applying a magnetic field. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 21-29, 1998
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    Smectic networks obtained from twin LC epoxy monomers - mechanical deformation of the smectic networks (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 31-38 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystals ; thermosets ; smectic epoxy ; nematic ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Deformation experiments were carried out for densely crosslinked smectic-like networks obtained from diepoxy monomers with twin mesogen architecture. For the initially unoriented smectic networks, the network could be aligned up to an orientation parameter of 0.35 by applying 8 MPa of external stress in the rubbery regime. X-ray diffraction measurements revealed that the deformed smectic network possesses both smectic-A like and smectic-C like structure. It is thought that after extension domains initially oriented parallel to the external stress displayed a smectic-A-like structure, whereas domains initially tilted with respect to the tensile direction showed a stress-induced smectic-C like structure. A smectic network oriented under a.c. electric fields with an orientation parameter of 0.4 had a smectic-A like structure and possessed linear elasticity in the rubbery regime. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 31-38, 1998
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    Morphological study on poly-p-phenylenebenzobisoxazole (PBO) fiber (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 39-48 
    Details
    ISSN: 0887-6266
    Keywords: poly-p-phenylenebenzobisoxazole ; X-ray scattering ; transmission electron microscopy ; Young's modulus ; tenacity ; crystal size ; orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies. Crystal size, orientation of the crystal, fibrils, microvoids, and fine structure were discussed. It was found that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal (160 Å) and the transverse (110 Å) directions. Crystal modulus estimated by extrapolation to perfect orientation on the plot of the fiber modulus as a function of fiber orientation (Northolt's method) shows discrepancy from the crystal modulus directly obtained by X-ray scattering. This discrepancy means that the Northolt's model is insufficient to describe the Young's modulus of PBO fiber. Microvoids elongated to the fiber direction were examined by small-angle X-ray scattering and transmission electron microscopic methods. The diameter of the microvoids was 20 Å to 30 Å and the fiber had a very thin microvoids-free layer (0.2 μm). Preferential orientation of the a-axis of crystal in the fiber was also confirmed. Summarizing these results, a structure model of the PBO fiber was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 39-48, 1998
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    Evaluation by Fourier Transform Infrared Spectroscopy of the different crystalline forms in syndiotactic polystyrene samples (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1055-1066 
    Details
    ISSN: 0887-6266
    Keywords: syndiotactic polystyrene ; polymorphism ; degree of crystallinity ; FTIR spectroscopy ; WAXS characterization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fourier transform infrared (FTIR) spectra of syndiotactic polystyrene (s-PS) semicrystalline samples have been examined by using the spectral subtraction approach. For the crystalline forms including trans-planar chains (trigonal α and orthorhombic β) a number of conformational and structural order effects, not previously described in the literature, have been identified. A method based on the results of the spectral subtraction analysis has been developed for the determination of the crystallinity degree and compared with the standard method based on the wide-angle X-ray diffraction patterns. The spectral subtraction analysis on FTIR spectra allows also an easy evaluation of the amount of α and β crystalline phases (often simultaneously present in melt-crystallized samples) although both contain chains in a same conformation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1055-1066, 1997
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    Nanoheterogeneity in PEO/PMMA blends probed by 129Xe-NMR (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2681-2688 
    Details
    ISSN: 0887-6266
    Keywords: NMR ; 129Xe ; blends ; PEO ; PMMA ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Xenon has been used as a structural probe of solid poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/PMMA) blends of concentrations 10/90 to 75/25. 129Xe-NMR spectra at 293 K show significant changes in line width and chemical shift as the blend composition is varied. The 129Xe spectra are interpreted in terms of exchange between amorphous single-phase PEO and PMMA domains. It is shown that a simple two-site exchange model can be used to calculate spectra which fit the experimental data over the whole concentration range. Xe exchange between blend subregions is demonstrated also by a two-dimensional NMR experiment. The PEO/PMMA results are compared to previously published poly(vinylidene fluoride)/PMMA 129Xe spectra. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2681-2688, 1997
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    Dynamic mechanical and dielectric relaxations in poly(monoethylphenyl itaconate) (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2749-2756 
    Details
    ISSN: 0887-6266
    Keywords: poly(monoethylphenyl itaconate) ; mechanical relaxation ; dielectric absorption ; dielectric loss modulus ; deconvolution method ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical and dielectric relaxational behavior of poly(monoethylphenyl itaconate) at different frequencies and temperatures was studied. Three relaxation zones are found. The dynamic mechanical response is dominated by a relaxation peak at room temperature, labeled β relaxation. Two prominent shoulders labelled as γ and α relaxations are observed. Because of the overlapping of the α and γ with the β relaxation, a deconvolution method to improve the understanding of these phenomena is proposed. In spite of the complexity of the experimental spectra, the proposed deconvolution method seems to be a convenient approach to interpret the relaxational behavior of this polymer. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2749-2756, 1997
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    FTIR spectroscopic study on crystallization process of poly(ethylene-2,6-naphthalate) (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2741-2747 
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    ISSN: 0887-6266
    Keywords: FTIR spectroscopy ; poly(ethylene-2,6-naphthalate) ; crystallization process ; induction period ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In situ Fourier transform infrared (FTIR) measurements were carried out to elucidate conformation changes occurring during the isothermal melt crystallization of poly(ethylene-2,6-naphthalate) (PEN). Based on the band assignments for the components of the amorphous, α-crystal form, and β-crystal form of PEN in film samples, the in situ data was analyzed in terms of the amorphous- and crystal-trans conformations. It was observed at a higher isothermal crystallization temperature that the formation of amorphous-trans conformations precedes the growth of crystals. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2741-2747, 1997
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    Transmission electron microscopy studies on selectively stained poly(aryl-ether-ether-ketone)/poly(ether-imide) semicrystalline blends (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2565-2570 
    Details
    ISSN: 0887-6266
    Keywords: Semicrystalline morphology ; lamellar structure ; poly(aryl-ether-ether-ketone) (PEEK) ; poly(ether-imide) (PEI) ; staining ; TEM ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
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    Interaction of the low-molecular weight salts with cationic polyelectrolytes (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2571-2581 
    Details
    ISSN: 0887-6266
    Keywords: cationic polyelectrolytes ; counterion binding ; viscosity ; conductivity ; salts ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interaction of several mono-, di-, and trivalent anions with cationic polyelectrolytes having different contents in N,N-dimethyl-2-hydroxypropylen ammonium chloride units (polymer A) or tertiary amine N-atoms and PEG (polymer PEGA) in the main chain was studied by viscosimetric and conductometric measurements. Both methods have shown a stronger interaction for tri- and bi- than for univalent counterions. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2571-2581, 1997
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    Effect of ion content in ionomer on the ion conductivity of polymer electrolytes based on the P(MMA-co-LiMA)/PEG/LiCF3SO3 blend (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 991-997 
    Details
    ISSN: 0887-6266
    Keywords: poly(methyl methacrylate-co-lithium methacrylate)(P(MMA-co-LiMA)) ; ionomer ; polymer electrolyte ; ion content ; ion conductivities ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have prepared polymer electrolytes composed of poly(methyl methacrylate-co-lithium methacrylate) ionomer (P(MMA-co-LiMA)), low molecular weight PEG, and LiCF3SO3 salt. The ion groups in P(MMA-co-LiMA) could enhance the miscibility between the MMA units and PEG in the polymer electrolytes. This miscibility enhancement made the pathway of ion transport less tortuous, and consequently led to the increase in ion conductivity. The maximum ambient ion conductivities in these systems were measured to be in the range of 10-4-10-5 S/cm. The polymer electrolytes became transparent at the higher ion content owing to the enhanced miscibility. The mechanical stability of the polymer electrolytes was also improved through the introduction of ion groups into the PMMA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 991-997, 1998
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    Structural investigation of polyaniline/Nylon 6 blends by small-angle neutron scattering and small- and wide-angle X-ray scattering (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2765-2774 
    Details
    ISSN: 0887-6266
    Keywords: polyaniline ; SANS ; Nylon 6 ; conducting blends ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure of blends of Nylon 6 with deuterated polyaniline emeraldine base (D-PANI-EB) and fully doped D-PANI salts (D-PANI-ES) formed from camphorsulfonic acid (CSA), methanesulfonic acid (MSA), or dodecyl benzenesulfonic acid (DBSA) were investigated by small-angle neutron (SANS) and X-ray scattering. The blends were formed from hexafluoro-2-propanol solutions and had volume fractions of 0.038, 0.20, and 0.40 for D-PANI/CSA, 0.20 and 0.40 for D-PANI/MSA, 0.24 and 0.44 for D-PANI/DBSA, and 0.07, 0.14, and 0.31 for D-PANI-EB. The SANS results are compared with a number of standard models for two-phase systems. No evidence was found for significant molecular mixing. In some cases the inverse power law model is in reasonable agreement with observations, and in the case of the lowest concentration of D-PANI/CSA there is an indication of mass fractal structure. This was not found at the higher concentrations. The results establish that the blends with the smaller more polar dopants CSA and MSA behave similarly and are unlike either the D-PANI/DBSA blends or those with D-PANI-EB. There is evidence that the simple picture of two pure phases is inadequate for these materials. With the exception of the D-PANI/DBSA blend which has a relatively low scattering contrast, the results indicate that the lower limit of volume fraction for application of SANS is a few percent D-PANI-ES in Nylon 6. X-ray scattering was used to demonstrate the presence of Nylon 6 lamellae and residual peaks attributable to the pure components. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2765-2774, 1997
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