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  • Analytical Chemistry and Spectroscopy  (8)
  • Inorganic Chemistry  (4)
  • 65K10  (3)
  • Alkaloids  (3)
  • cystic fibrosis  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 56 (1992), S. 189-222 
    ISSN: 1436-4646
    Keywords: 65H10 ; 65K05 ; 65K10 ; Linearℓ 1 estimation ; linear programming ; interior-point algorithm ; simplex method ; least absolute value regression ; affine scaling method ; Karmarkar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Recently, various interior point algorithms related to the Karmarkar algorithm have been developed for linear programming. In this paper, we first show how this “interior point” philosophy can be adapted to the linear ℓ1 problem (in which there are no feasibility constraints) to yield a globally and linearly convergent algorithm. We then show that the linear algorithm can be modified to provide aglobally and ultimatelyquadratically convergent algorithm. This modified algorithm appears to be significantly more efficient in practise than a more straightforward interior point approach via a linear programming formulation: we present numerical results to support this claim.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 45 (1989), S. 373-406 
    ISSN: 1436-4646
    Keywords: 65K05 ; 90C20 ; 65K10 ; 65F30 ; Quadratic programming ; large sparse minimization ; active set methods ; trust region methods ; sparse Cholesky factorization updates ; simple bounds ; box constraints
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We show how a direct active set method for solving definite and indefinite quadratic programs with simple bounds can be efficiently implemented for large sparse problems. All of the necessary factorizations can be carried out in a static data structure that is set up before the numeric computation begins. The space required for these factorizations is no larger than that required for a single sparse Cholesky factorization of the Hessian of the quadratic. We propose several improvements to this basic algorithm: a new way to find a search direction in the indefinite case that allows us to free more than one variable at a time and a new heuristic method for finding a starting point. These ideas are motivated by the two-norm trust region problem. Additionally, we also show how projection techniques can be used to add several constraints to the active set at each iteration. Our experimental results show that an algorithm with these improvements runs much faster than the basic algorithm for positive definite problems and finds local minima with lower function values for indefinite problems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 53 (1992), S. 17-44 
    ISSN: 1436-4646
    Keywords: 65H10 ; 65K05 ; 65K10 ; Constrained optimization ; equality constraints ; numerical optimization ; quasi-Newton method ; secant method ; sequential quadratic programming ; SQP-method ; augmented Lagrangian method ; penalty function methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We derive new quasi-Newton updates for the (nonlinear) equality constrained minimization problem. The new updates satisfy a quasi-Newton equation, maintain positive definiteness on the null space of the active constraint matrix, and satisfy a minimum change condition. The application of the updates is not restricted to a small neighbourhood of the solution. In addition to derivation and motivational remarks, we discuss various numerical subtleties and provide results of numerical experiments.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Glycoconjugate journal 17 (2000), S. 617-626 
    ISSN: 1573-4986
    Keywords: α1,3fucose ; α1,6fucose ; sialic acid ; polyα2,8sialic acid ; surface membrane glycoforms ; cystic fibrosis ; lactosylated polylysine gene therapy vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Terminal glycosylation has been a recurring theme of the laboratory. In cystic fibrosis (CF), decreased sialic acid and increased fucosyl residues in α1,3 position to antennary N -acetyl glucosamine is the CF glycosylation phenotype. The glycosylation phenotype is reversed by transfection of CF airway cells with wtCFTR. In neuronal cells, polymers of α2,8sialyl residues are prominent in oligodendrocytes and human neuroblastoma. These findings are discussed in relationship to early studies in our laboratories and those of other investigators. The potential extension of these concepts to future clinical therapeutics is presented.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4986
    Keywords: glycosylation ; cystic fibrosis ; airway epithelial cells ; α1,3fucose ; sialic acid ; CFTR ; CFTR transfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cystic fibrosis (CF) has a characteristic glycosylation phenotype usually expressed as a decreased ratio of sialic acid to fucose. The glycosylation phenotype was found in CF/T1 airway epithelial cells (ΔF508/ΔF508). When these cells were transfected and were expressing high amounts of wtCFTR, as detected by Western blot analysis and in situ hybridization, the cell membrane glycoconjugates had an increased sialic acid content and decreased fucosyl residues in α1,3/4 linkage to antennary N[emsp4 ]-acetyl glucosamine (Fucα1,3/4GlcNAc). After the expression of wtCFTR decreased, the amount of sialic acid and Fucα1,3/4GlcNAc returned to levels shown by the parent CF cells. Sialic acid was measured by chemical analysis and Fucα1,3/4GlcNAc was detected with a specific α1,3/4 fucosidase. CF and non-CF airway cells in primary culture also had a similar reciprocal relationship between fucosylation and sialylation. It is possible that the glycosylation phenotype is involved in the pathogenesis of CF lung disease by facilitating bacterial colonization and leukocyte recruitment.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-1561
    Keywords: Alkaloids ; coccinellines ; decahydroquinolines ; indolizidines ; pyrrolidines ; pyrrolizidines ; dendrobatid frogs ; myrmicine ants ; coccinellid beetles ; millipedes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Neotropical poison frogs (Dendrobatidae) contain a wide variety of lipophilic alkaloids, apparently accumulated unchanged into skin glands from dietary sources. Panamanian poison frogs (Dendrobates auratus) raised in a large, screened, outdoor cage and provided for six months with leaf-litter from the frog's natural habitat, accumulated a variety of alkaloids into the skin. These included two isomers of the ant pyrrolizidine 251K; two isomers of the 3,5-disubstituted indolizidine 195B; an alkaloid known to occur in myrmicine ants; another such indolizidine, 211E; two pyrrolidines, 197B and 223N, the former known to occur in myrmicine ants; two tricyclics, 193C and 219I, the former known to occur as precoccinelline in coccinellid beetles; and three spiropyrrolizidines, 222, 236, and 252A, representatives of an alkaloid class known to occur in millipedes. The alkaloids 211E, 197B, and 223N appear likely to derive in part from ants that entered the screened cage. In addition, the frog skin extracts contained trace amounts of four alkaloids, 205D, 207H, 219H, and 231H, of unknown structures and source. Wild-caught frogs from the leaf-litter site contained nearly 40 alkaloids, including most of the above alkaloids. Pumiliotoxins and histrionicotoxins were major alkaloids in wild-caught frogs, but were absent in captive-raised frogs. Ants microsympatric with the poison frog at the leaf-litter site and at an island site nearby in the Bay of Panamá were examined for alkaloids. The decahydroquinoline (−)-cis-195A and two isomers of the pyrrolizidine 251K were found to be shared by microsympatric myrmicine ants and poison frogs. The proportions of the two isomers of 251K were the same in ant and frog.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 20 (1994), S. 943-955 
    ISSN: 1573-1561
    Keywords: Alkaloids ; indolizidines ; pyrrolizidines ; histrionicotoxins ; coccinellines ; dendrobatid frogs ; insects ; millipedes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A wide range of alkaloids, many of which are unknown elsewhere in nature, occur in skin of frogs. Major classes of such alkaloids in dendrobatid frogs are the batrachotoxins, pumiliotoxins, histrionicotoxins, gephyrotoxins, and decahydroquinolines. Such alkaloids are absent in skin of frogs (Dendrobates auratus) raised in Panama on wingless fruit flies in indoor terraria. Raised on leaf-litter arthropods that were collected in a mainland site, such terraria-raised frogs contain tricyclic alkaloids including the beetle alkaloid precoccinelline, 1,4-disubstituted quinolizidines, pyrrolizidine oximes, the millipede alkaloid nitropolyzonamine, a decahydroquinoline, a gephyrotoxin, and histrionicotoxins. The profiles of these alkaloids in the captive-raised frogs are closer to the mainland population ofDendrobates auratus at the leaf-litter site than to the parent population ofDendrobates auratus from a nearby island site. Extracts of a seven-month sampling of leaf-litter insects contained precoccinelline, pyrrolizidine oxime236 (major), and nitropolyzonamine (238). The results indicate a dietary origin for at least some “dendrobatid alkaloids,” in particular the pyrrolizidine oximes, the tricyclic coccinellines, and perhaps the histrionicotoxins and gephyrotoxins.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 52 (1907), S. 368-396 
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es wurde eine bequeme Methode zur elektrolytischen Darstellung der Vanadisalze ausgearbeitet.Es wurde das elektromotorische Verhalten gelöster Vanadinsalze in verschiedenen Oxydationsstufen untersucht.Es wurde qualitativ das Verhalten der Vanadinsalze zu verschiedenen Oxydations- und Reduktionsmitteln, sowie zu Bikarbonatlösungen untersucht.Es wurde quantitativ die Reaktionsgeschwindigkeit zwischen Vanadi- und Silbersulfat, sowie der katalytische Einflufs von Eisen- und Kupfersalzen auf diese Reaktion untersucht.Bei Gegenwart von Kupfersalzen wird in dieser Reaktion eine Anfangsbeschleunigung beobachtet, die mit einer amorphen Ausscheidung des Silbers Hand in Hand geht.Es wurden die qualitativen Methoden zum Nachweis von Vanadi- und Vanadoverbindungen kritisch besprochen.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Glycoconjugate journal 1 (1994), S. 263-270 
    ISSN: 1573-4986
    Keywords: airway epithelial cells ; CFTR ; cystic fibrosis ; α-l-fucosidase ; fucosylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Altered glycosylation is a phenotypic characteristic of cystic fibrosis (CF), and some of the alterations are summarized. The lungs are the site of the lethal pathology of the disease. Therefore, two of the characteristics were examined in CF and non-CF immortalized airway epithelial cell lines (AEC). The activity of α-l-fucosidase was elevated (280%) in CF AEC when compared with non-CF AEC, whereas the activities of the other lysosomal enzymes which were examined were similar in both cell types. α-l-Fucosidase activity was transiently increased in the non-CF cells after treatment with Brefeldin A (BFA) for 6 h. Thus BFA caused the normal cells to express a phenotypic characteristic of CF. Glycopeptides from the CF and non-CF AECs metabolically labeled withl-[3H]fucose were examined for binding to lentil lectin-Sepharose. A higher percentage of CF glycopeptides bound to lentil lectin, 43% compared with 23% for non-CF control. In addition a higher percentage of CF glycopeptides were bound tightly to lentil lectin and required 0.2M α-methylmannoside to be eluted. This species of tightly bound glycopeptides increased dramatically to 77% from 46% when the CF AEC were treated with BFA. In contrast, the non-CF cell glycopeptides had a minor decrease in tightly bound glycopeptides to 26% from 33% after BFA treatment. Thus, the CF AEC showed fucosylation alteration observed previously for other CF cells and tissue.
    Type of Medium: Electronic Resource
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