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  • Polymer and Materials Science  (1,747)
  • Mice  (662)
  • 2005-2009  (476)
  • 1990-1994  (1,891)
  • 1945-1949  (42)
  • 1935-1939
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  • 1
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    The genomic landscapes of human breast and colorectal cancers (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-10-13
    Description: Human cancer is caused by the accumulation of mutations in oncogenes and tumor suppressor genes. To catalog the genetic changes that occur during tumorigenesis, we isolated DNA from 11 breast and 11 colorectal tumors and determined the sequences of the genes in the Reference Sequence database in these samples. Based on analysis of exons representing 20,857 transcripts from 18,191 genes, we conclude that the genomic landscapes of breast and colorectal cancers are composed of a handful of commonly mutated gene "mountains" and a much larger number of gene "hills" that are mutated at low frequency. We describe statistical and bioinformatic tools that may help identify mutations with a role in tumorigenesis. These results have implications for understanding the nature and heterogeneity of human cancers and for using personal genomics for tumor diagnosis and therapy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wood, Laura D -- Parsons, D Williams -- Jones, Sian -- Lin, Jimmy -- Sjoblom, Tobias -- Leary, Rebecca J -- Shen, Dong -- Boca, Simina M -- Barber, Thomas -- Ptak, Janine -- Silliman, Natalie -- Szabo, Steve -- Dezso, Zoltan -- Ustyanksky, Vadim -- Nikolskaya, Tatiana -- Nikolsky, Yuri -- Karchin, Rachel -- Wilson, Paul A -- Kaminker, Joshua S -- Zhang, Zemin -- Croshaw, Randal -- Willis, Joseph -- Dawson, Dawn -- Shipitsin, Michail -- Willson, James K V -- Sukumar, Saraswati -- Polyak, Kornelia -- Park, Ben Ho -- Pethiyagoda, Charit L -- Pant, P V Krishna -- Ballinger, Dennis G -- Sparks, Andrew B -- Hartigan, James -- Smith, Douglas R -- Suh, Erick -- Papadopoulos, Nickolas -- Buckhaults, Phillip -- Markowitz, Sanford D -- Parmigiani, Giovanni -- Kinzler, Kenneth W -- Velculescu, Victor E -- Vogelstein, Bert -- CA 43460/CA/NCI NIH HHS/ -- CA 57345/CA/NCI NIH HHS/ -- CA109274/CA/NCI NIH HHS/ -- CA112828/CA/NCI NIH HHS/ -- CA121113/CA/NCI NIH HHS/ -- CA62924/CA/NCI NIH HHS/ -- GM070219/GM/NIGMS NIH HHS/ -- GM07309/GM/NIGMS NIH HHS/ -- P30-CA43703/CA/NCI NIH HHS/ -- RR017698/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 2007 Nov 16;318(5853):1108-13. Epub 2007 Oct 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institute at Johns Hopkins Kimmel Cancer Center, Baltimore, MD 21231, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17932254" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Breast Neoplasms/*genetics/metabolism ; Cell Line ; Chromosome Mapping ; Colorectal Neoplasms/*genetics/metabolism ; Computational Biology ; DNA, Neoplasm ; Databases, Genetic ; Genes, Neoplasm ; Genome, Human ; Humans ; Metabolic Networks and Pathways/genetics ; Mice ; Mutation ; Neoplasm Proteins/genetics/metabolism ; Sequence Analysis, DNA
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
    Electronic Resource
    Electronic Resource
    Poly(dimethylsiloxane)-poly(ethylene oxide)-heparin block copolymers III: Surface and bulk compositional differences (1990)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 547-571 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previously observed bioactivity of poly(dimethylsiloxane)-poly(ethyelene oxide)-heparin (PDMS-PEO-Hep) triblock copolymers has prompted studies of the surface and bulk character of this copolymer using angular-dependent electron spectroscopy for chemical analysis (ADESCA), static secondary mass spectroscopy (SIMS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Because the low-energy PDMS phase dominates surfaces of this copolymer when solvent cast under air or vacuum conditions, attempts were made to explain surface restructuring and rearrangements induced in hydrated or aqueous environments that permit surface accessibility and bioactivity of heparin moieties. Based on comparisons with PDMS, PEO, and heparin homopolymers, PEO/heparin blends, and an unheparinized PDMS-PEO diblock copolymer, PDMS-PEO-heparin demonstrates both phase-mixed and phase-separated regions in DSC analysis. During annealing cycles above the Tg values of the copolymer constituents, phase-mixed regions become increasingly phase separated and PEO enriched. TGA analysis confirmed the presence of block copolymer constituents and presented evidence of intermolecular segmental interactions, hence phase-mixing in the copolymers. ADESCA analysis indicates that the outer 5 Å of both the PDMS-PEO and PDMS-PEO-Hep copolymers is essentially pure PDMS. However, significant amounts of PEO are detected 5 to 20 Å below the surface. Static SIMS also detects the presence of PDMS at the surfaces of the PDMS-PEO and PDMS-PEO-Hep copolymers. Compositional models based on ADESCA, SIMS, and DSC data are presented for desiccated and hydrated copolymer surfaces.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820240503
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  • 3
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    Common Kibra alleles are associated with human memory performance (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-10-21
    Description: Human memory is a polygenic trait. We performed a genome-wide screen to identify memory-related gene variants. A genomic locus encoding the brain protein KIBRA was significantly associated with memory performance in three independent, cognitively normal cohorts from Switzerland and the United States. Gene expression studies showed that KIBRA was expressed in memory-related brain structures. Functional magnetic resonance imaging detected KIBRA allele-dependent differences in hippocampal activations during memory retrieval. Evidence from these experiments suggests a role for KIBRA in human memory.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Papassotiropoulos, Andreas -- Stephan, Dietrich A -- Huentelman, Matthew J -- Hoerndli, Frederic J -- Craig, David W -- Pearson, John V -- Huynh, Kim-Dung -- Brunner, Fabienne -- Corneveaux, Jason -- Osborne, David -- Wollmer, M Axel -- Aerni, Amanda -- Coluccia, Daniel -- Hanggi, Jurgen -- Mondadori, Christian R A -- Buchmann, Andreas -- Reiman, Eric M -- Caselli, Richard J -- Henke, Katharina -- de Quervain, Dominique J-F -- P30AG19610/AG/NIA NIH HHS/ -- R01MH057899/MH/NIMH NIH HHS/ -- U01-HL086528-01/HL/NHLBI NIH HHS/ -- U24NS051872/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 2006 Oct 20;314(5798):475-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Psychiatry Research, University of Zurich, Zurich 8057, Switzerland. papas@bli.unizh.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17053149" target="_blank"〉PubMed〈/a〉
    Keywords: Adolescent ; Adult ; Alleles ; Animals ; Attention ; Brain/*physiology ; Brain Chemistry ; Calcium-Binding Proteins/genetics ; Cohort Studies ; Female ; Gene Expression ; Genotype ; Haplotypes ; Hippocampus/chemistry/*physiology ; Humans ; Intracellular Signaling Peptides and Proteins ; Magnetic Resonance Imaging ; Male ; Membrane Proteins/genetics ; *Memory ; Mice ; Middle Aged ; Phosphoproteins ; *Polymorphism, Single Nucleotide ; Proteins/analysis/*genetics/*physiology ; Reverse Transcriptase Polymerase Chain Reaction ; Switzerland ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-04-08
    Description: Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1482474/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1482474/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Habashi, Jennifer P -- Judge, Daniel P -- Holm, Tammy M -- Cohn, Ronald D -- Loeys, Bart L -- Cooper, Timothy K -- Myers, Loretha -- Klein, Erin C -- Liu, Guosheng -- Calvi, Carla -- Podowski, Megan -- Neptune, Enid R -- Halushka, Marc K -- Bedja, Djahida -- Gabrielson, Kathleen -- Rifkin, Daniel B -- Carta, Luca -- Ramirez, Francesco -- Huso, David L -- Dietz, Harry C -- K08 HL067056/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 2006 Apr 7;312(5770):117-21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute and Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16601194" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenergic beta-Antagonists/administration & dosage/therapeutic use ; Angiotensin II Type 1 Receptor Blockers/administration & dosage/*therapeutic use ; Animals ; Antibodies/immunology ; Aorta/pathology ; Aortic Aneurysm/etiology/*prevention & control ; *Disease Models, Animal ; Elastic Tissue/pathology ; Female ; Losartan/administration & dosage/*therapeutic use ; Lung/pathology ; Lung Diseases/drug therapy/pathology ; Marfan Syndrome/complications/*drug therapy/metabolism/pathology ; Mice ; Microfilament Proteins/genetics ; Mutation ; Neutralization Tests ; Pregnancy ; Pregnancy Complications/drug therapy ; Propranolol/administration & dosage/therapeutic use ; Pulmonary Alveoli/pathology ; Receptor, Angiotensin, Type 1/metabolism ; Signal Transduction ; Transforming Growth Factor beta/antagonists & inhibitors/immunology/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Pulsatile stimulation determines timing and specificity of NF-kappaB-dependent transcription (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-04-11
    Description: The nuclear factor kappaB (NF-kappaB) transcription factor regulates cellular stress responses and the immune response to infection. NF-kappaB activation results in oscillations in nuclear NF-kappaB abundance. To define the function of these oscillations, we treated cells with repeated short pulses of tumor necrosis factor-alpha at various intervals to mimic pulsatile inflammatory signals. At all pulse intervals that were analyzed, we observed synchronous cycles of NF-kappaB nuclear translocation. Lower frequency stimulations gave repeated full-amplitude translocations, whereas higher frequency pulses gave reduced translocation, indicating a failure to reset. Deterministic and stochastic mathematical models predicted how negative feedback loops regulate both the resetting of the system and cellular heterogeneity. Altering the stimulation intervals gave different patterns of NF-kappaB-dependent gene expression, which supports the idea that oscillation frequency has a functional role.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785900/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785900/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ashall, Louise -- Horton, Caroline A -- Nelson, David E -- Paszek, Pawel -- Harper, Claire V -- Sillitoe, Kate -- Ryan, Sheila -- Spiller, David G -- Unitt, John F -- Broomhead, David S -- Kell, Douglas B -- Rand, David A -- See, Violaine -- White, Michael R H -- BB/C007158/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/C008219/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/C520471/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/D010748/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/E004210/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/E012965/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/F005938/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBC0071581/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBC0082191/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBC5204711/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBD0107481/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBF0059381/Biotechnology and Biological Sciences Research Council/United Kingdom -- G0500346/Medical Research Council/United Kingdom -- G0500346(73596)/Medical Research Council/United Kingdom -- New York, N.Y. -- Science. 2009 Apr 10;324(5924):242-6. doi: 10.1126/science.1164860.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Cell Imaging, School of Biological Sciences, Bioscience Research Building, Crown Street, Liverpool, L69 7ZB, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19359585" target="_blank"〉PubMed〈/a〉
    Keywords: Active Transport, Cell Nucleus ; Animals ; Cell Line ; Cell Line, Tumor ; Cell Nucleus/metabolism ; Cytoplasm/metabolism ; Feedback, Physiological ; *Gene Expression ; Humans ; I-kappa B Proteins/metabolism ; Mice ; Models, Biological ; Models, Statistical ; NF-kappa B/*metabolism ; Phosphorylation ; Recombinant Fusion Proteins/metabolism ; Stochastic Processes ; Transcription Factor RelA/*metabolism ; *Transcription, Genetic ; Transfection ; Tumor Necrosis Factor-alpha/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Ribosomal protein S6 kinase 1 signaling regulates mammalian life span (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-10-03
    Description: Caloric restriction (CR) protects against aging and disease, but the mechanisms by which this affects mammalian life span are unclear. We show in mice that deletion of ribosomal S6 protein kinase 1 (S6K1), a component of the nutrient-responsive mTOR (mammalian target of rapamycin) signaling pathway, led to increased life span and resistance to age-related pathologies, such as bone, immune, and motor dysfunction and loss of insulin sensitivity. Deletion of S6K1 induced gene expression patterns similar to those seen in CR or with pharmacological activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), a conserved regulator of the metabolic response to CR. Our results demonstrate that S6K1 influences healthy mammalian life-span and suggest that therapeutic manipulation of S6K1 and AMPK might mimic CR and could provide broad protection against diseases of aging.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Selman, Colin -- Tullet, Jennifer M A -- Wieser, Daniela -- Irvine, Elaine -- Lingard, Steven J -- Choudhury, Agharul I -- Claret, Marc -- Al-Qassab, Hind -- Carmignac, Danielle -- Ramadani, Faruk -- Woods, Angela -- Robinson, Iain C A -- Schuster, Eugene -- Batterham, Rachel L -- Kozma, Sara C -- Thomas, George -- Carling, David -- Okkenhaug, Klaus -- Thornton, Janet M -- Partridge, Linda -- Gems, David -- Withers, Dominic J -- BBS/E/B/0000C236/Biotechnology and Biological Sciences Research Council/United Kingdom -- BBS/E/B/0000M979/Biotechnology and Biological Sciences Research Council/United Kingdom -- G0800339/Medical Research Council/United Kingdom -- G108/551/Medical Research Council/United Kingdom -- MC_U117531708/Medical Research Council/United Kingdom -- MC_U120027537/Medical Research Council/United Kingdom -- MC_U120097114/Medical Research Council/United Kingdom -- Biotechnology and Biological Sciences Research Council/United Kingdom -- Medical Research Council/United Kingdom -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 2009 Oct 2;326(5949):140-4. doi: 10.1126/science.1177221.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Healthy Ageing, Centre for Diabetes and Endocrinology, Department of Medicine, University College London, London WC1E 6JJ, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19797661" target="_blank"〉PubMed〈/a〉
    Keywords: AMP-Activated Protein Kinases/metabolism ; Adipose Tissue, White/metabolism ; Aging/*physiology ; Animals ; Bone Density ; Caloric Restriction ; Female ; Gene Deletion ; Gene Expression ; Gene Expression Regulation ; Insulin/metabolism ; Liver/metabolism ; Longevity/*physiology ; Male ; Mice ; Mice, Inbred C57BL ; Motor Activity ; Muscle, Skeletal/metabolism ; Protein Kinases/metabolism ; Ribosomal Protein S6 Kinases, 90-kDa/genetics/*metabolism ; *Signal Transduction ; T-Lymphocyte Subsets/immunology ; TOR Serine-Threonine Kinases ; Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Melanin-concentrating hormone: A structural and conformational study based on synthesis, biological activity, high-field nmr, and molecular modeling techniques (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 609-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290314
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  • 8
    Electronic Resource
    Electronic Resource
    Model filled polymers. I. Synthesis of crosslinked monodisperse polystyrene beads (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1909-1921 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monodisperse crosslinked polystyrene beads of varied size and crosslink density are prepared by emulsion copolymerization of styrene and divinylbenzene in the absence of emulsifier. Tumbling and internally stirred reactors were used for synthesis, with minimal agglomeration at at least 0.22 wt % potassium persulfate and up to 10% by weight of styrene in aqueous emulsion in the absence of oxygen. Particle sizes decreased from 800 to 200 nm on raising the polymerization temperature from 60 to 95°C. The glass transition temperature of the beads increased from 104.4 to 133°C by the inclusion of up to 10% by weight of divinylbenzene. The thermal stability of the beads was higher for peroxide than for persulfate initiation. The crosslink density estimated from the degree of swelling was about one third that expected from stoichiometry. The polystyrene beads are used as filler particles in polymer composites.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280722
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  • 9
    Electronic Resource
    Electronic Resource
    Chain orientation and anisotropies in optical and dielectric properties in thin films of stiff polyimides (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1321-1327 
    Details
    ISSN: 0887-6266
    Keywords: polyimides. stiff, optical and dielectric properties in their films of ; optical anisotropy and chain orientation stiff polyimide thin films ; dielectric properties of stiff polyimide thin films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin films of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, ultraviolet-visible (UV-VIS), infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n∥ = 1.806 and the out-of-plane index n⊥ = 1.589 at 1064 nm wavelength. No discernible effect of the film thickness on this optical anisotropy is found between films of ca. 2.1 and ca. 7.8 μm thickness. This large birefringence is attributed to the preferential orientation of the biphenyltetracarboximide moieties with their planes parallel to the film surface, coupled with the strong preference of BPDA-PDA chains to align along the film plane. The frequency dispersion of the in-plane refractive index n∥ is consistent with the results calculated by the Lorentz-Lorenz equation from the UV-visible spectrum exhibiting several absorption bands in the 170-500 nm region. The contribution from the IR absorption in the range 7000-400 cm,-1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.046 to the in-plane refractive index n∥. Tilt-angle-dependent polarized IR results indicate nearly the same increase for the out-of-plane index n⊥. Application of the Maxwell relation then leads to the out-of-plane dielectric constant ε⊥ ≃ 2.7 at 1.2 × 1013 Hz, as compared with the measured value of ca. 3.0 at 106 Hz. Assuming this small difference to remain the same for the in-plane dielectric constants ε∥, we obtain a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant ε∥ ≃ 3.4 at 1.2 × 1013 Hz, and ε∥ ≃ 3.7 at 106 Hz. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090301203
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  • 10
    Electronic Resource
    Electronic Resource
    Crystallinity and lateral crystallite size of different UHMW PE materials (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 863-866 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70-75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15-25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420332
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