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  • Articles  (86)
  • Physics  (58)
  • Genetics  (28)
  • Wiley-Blackwell  (86)
  • International Union of Crystallography
  • 1985-1989  (86)
  • 1955-1959
  • 1940-1944
  • 1
    ISSN: 0192-253X
    Keywords: tubulin genes ; microtubules ; Arabidopsis thaliana ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Microtubules are important components of the cytoskeleton of plant cells and play key roles in plant growth and morphogenesis. Recent molecular studies have begun to elucidate the structure and expression of plant genes coding for the major components of microtubules, α- and β-tubulin. Tubulin amino acid sequences deduced from the DNA sequences of eight higher plant tubulin genes are 79-87% homologous with constitutively expressed mammalian tubulins. The genome of the model plant system Arabidopsis thaliana contains four dispersed α-tubulin sequences and at least seven β-tubulin sequences, only two of which appear to be linked. Of the five A. thaliana genes whose expression has been analyzed, the transcripts of one α-tubulin and one β-tubulin gene are constitutively expressed in roots, leaves, and flowers. A second α-tubulin gene is expressed predominately in flowers; the transcripts of the second and third β-tubulin genes are found predominately in leaves or in roots, respectively.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 1997-2003 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of butadiene by lithium-based initiators in aliphatic hydrocarbon solvents in the presence of dipiperidinoethane gives a highly 1,2 structure. This system was studied to determine the factors that govern the structure. The effect of this complexing agent on the kinetics of propagation, the microstructure of the polymer, and the ultraviolet spectrum of the active chain end was measured. The results suggest that more than one solvated species form, all giving highly 1,2 polymer structures, but that a solvate containing one chain end with one dipiperidinoethane molecule is the principal reacting species which gives close to 100% 1,2 structure. This reacting center has a high proportion of trans-structure in the allyllic ion, únlike most complexed active chain ends, which are often highly cis. It is this transstructure in the ion that is thought to be responsible for the polymer structure.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0192-253X
    Keywords: mental retardation ; Down syndrome ; cholinergic neurons ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In this study, we examined the neurochemical profiles of selected brain regions (cerebral hemispheres, diencephalon/brainstem) in fetal (day 14 to 18 gestation) trisomy 19 (Ts19) mice. The neurochemical characteristics we observed in Ts19 mice were quite different from those we observed previously in Ts16 mice. Choline acetyltransferase (ChAT) activity was reduced significantly in the cerebral hemispheres, but not in the brainstem/diencephalon, of the fetal Ts19 mouse brain, suggesting a selective vulnerability of telencephalic cholinergic neurons. Additionally, the activity of glutamic acid decarboxylase (GAD) was reduced significantly in both hemispheres and diencephalon/brainstem of late gestation Ts19 fetuses, suggesting a selective vulnerability of GABAergic neurons as well. While the levels of catecholaminergic and dopaminergic markers were reduced significantly at late gestational ages, the relative rate of turnover of dopamine (DA), measured by the ratio of DOPAC/DA, was elevated significantly in Ts19 mice. Neither reduction in the thickness of various cellular zones of the cerebral cortex nor reduced cell density of the cerebral cortex accounts for the alterations in neurochemical parameters observed in Ts19 mice. These results suggest that the effects of the triplication of specific genes on the respective chromosomes, rather than a generalized disruption of developmental homeostasis resulting from extra chromosomal material, may produce selective alterations in neurochemical and neuroanatomical markers observed in these two mouse trisomies.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 387-404 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The self-diffusion coefficient D of paraffin and polyethylene melts - covering the range between N = 19 and 103 where N is the number of monomeric units - was measured by the pulsed-magnetic-field-gradient NMR method for diffusion times between 3 ms and 1 s. For the paraffins, D is proportional to N-2 though the molecular weights are smaller than the critical molecular weight for entanglement. In polyethylene, melts a strong dependence of the diffusion coefficient on the diffusion time is observed, whereas no such dependence is found in paraffin melts. A mathematical formalism for describing spin-echo attenuation in terms of a velocity autocorrelation function is shown to yield qualitative agreement with the experimental results.
    Additional Material: 8 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1869-1881 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Far-infrared spectra of a series of un-neutralized and neutralized lightly sulfonated polystyrenes with varying sulfonation levels have been investigated to seek spectroscopic evidence for microphase separation known to control the physical properties of these polymers. Broad, strong absorbance bands, not found in the spectrum of unmodified polystyrene, are observed in the spectra of the sulfonated analogs. The effects on the far-infrared spectra both of sulfonation level and of the mass and charge of the neutralizing cation are discussed in terms of cation motion and the formation of ion-rich domains.
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  • 6
    ISSN: 0192-253X
    Keywords: Agrobacterium insertion mutants ; hormone equilibria ; differentiation ; dedifferentiation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A series of experiments are presented that have been performed to observe the interactions between Agrobacterium tumefaciens strains mutated in the T-DNA genes involved in indoleacetic acid and cytokinin biosynthesis and several Nicotiana species and hybrids. Infections were induced on leaf cuttings of Nicotiana debneyi, N. knightiana, N. clevelandii, N. bigelovii var bigelovii, N. bigelovii var quadrivalvis, N. glauca, N. langsdorffii, the amphidiploid tumorous hybrid N. glauca × N. langsdorffii, and a nontumorous mutant of it. The effect of deletions of the Ti plasmid varied according to plant genotype. Insertion mutants in iaaM and iaaH suppressed tumor formation in N. langsdorffii, reduced it in N. bigeloviivar quadrivalvis, had no effect in N. glauca and the two amphidiploid hybrids, and promoted tumorigenesis when compared to the wild-type Agrobacterium strain B6S3 in N. bigelovii N. debneyi, and N. knightiana. The same mutations induced shoot formation in N. glauca, increased it in N. debneyi, and suppressed root formation in N. knightiana. On the other hand, an insertion mutation of the isopentenyl transferase gene (ipt-) had no effect in N. bigelovii var quadrivalvis, N. debneyi, the tumorous hybrid, suppressed tumor formation in N. langsdorffii, and inhibited it in N. glauca, the nontumorous hybrid, N. bigelovii var bigelovii, and N. knightiana. Insertion in ipt suppressed shoot formation in the nontumorous hybrid and inhibited it in the nontumorous amphidiploid and N. debneyi, while promoting root formation in N. glauca and N. debneyi.The suggestion of the existence of specific hormone equilibria necessary for the shift to each morphogenetic pattern was supported by experiments with exogenous hormone treatments of three genotypes (N. glauca, N. langsdorffii, and the nontumorous N. glauca × N. langsdorffii).
    Additional Material: 4 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 2931-2945 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thin films of cured MY720/DDS epoxy resins were treated with blocking reagents for hydroxyl, amine, and epoxide functional groups. Infrared spectroscopy (IR) and differential scanning calorimetry (DSC) were used to monitor the progress of the reaction. Treated films were soaked in distilled water at 30°C for 720 h, and the corresponding moisture absorption determined gravimetrically. Samples treated with N-methyl-N-t-butyldimethylsilyl trifluroacetamide (MTBSTFA) containing 1% t-butyldimethylchlorosilane (TBDMCS) in dimethylsulfoxide (DMSO) at 30°C showed a maximum reduction in the IR peak at 3400 cm-1 (OH and NH) of 39% and a 100% reduction in the epoxide peak at 904 cm, -1. The moisture absorption was 1.9%, a reduction of 58% compared to the untreated films (ca. 4.5%). The reactions show dependencies on time and temperature and are diffusion controlled. Samples treated with trimethylsilyl isocyanate (TMSI) in DMSO a 70°C showed 72% reduction in the 3400 cm-1 IR peak; DSC thermograms do not show an exothermic energy, suggesting that all epoxide groups reacted. These reactions are primarily dependent on time and temperature. The moisture absorption of TMSI treated samples was 1.0% (75% reduction). Samples were also treated with m-trifluoromethyl phenyliscyanate (MTFPI). The reduction in the IR peak at 3400 cm-1 was 9%, but the moisture absorption was 2.4% - a reduction of 47%.
    Additional Material: 12 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 569-573 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 1771-1785 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of saturated liquid densities and ethylene solubilities in ethylene - polyethylene systems up to 26.1 MPa and 493.1 K were obtained using a new variable-volume static cell after a careful investigation of the influence of inhibitors of polymerization of ethylene under experimental conditions.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 2177-2195 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyamides were synthesized at -60°, -40°, -20°, and 0°C from sebacyl bisketene and 1,6-hexamethylenediamine in either acetone or methylene chloride. At the lower reaction temperatures oligomers predominated in solution but at 0°C the product was crosslinked. The polyamides were subjected to m-cresol extraction at elevated temperatures for up to 14 days. The m-cresol soluble and insoluble fractions were characterized by weight, infrared spectroscopy, dilute solution viscosity, and gel permeation chromatography. Infrared analysis of the soluble and insoluble portions showed the degree of branching of the polyamide, identified the branching point at the secondary amide proton position, and gave an indication of the degree of branching required before insoluble products resulted. Dilute solution viscosity and gel permeation chromatography were used to demonstrate the existence of low molecular weight (Mw) oligomer species in the soluble portion. Differential scanning calorimetry experiments revealed that polyamides synthesized below their glass transition temperature would not crystallize which resulted in abnormal thermal characteristics. Annealing at elevated temperatures allowed crystallization to occur and the expected thermal character to develop.
    Additional Material: 14 Ill.
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