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  • General Chemistry  (77,717)
  • Witterung
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  • 1
    Publication Date: 2024-02-26
    Description: Identifcation of ontogenetic age classes plays an important role in the felds of zoology, palaeontology and archaeology, where accurate age classifcations of (sub)fossil remains are a crucial component for the reconstruction \nof past life. Textural ageing\xe2\x80\x94the identifcation of age-related bone surface textures\xe2\x80\x94provides a size-independent \nmethod for age assessment of vertebrate material. However, most of the work so far is limited to qualitative results. \nWhile qualitative approaches provide helpful insights on textural ageing patterns, they are heavily subject to observer \nbias and fall short of quantitative data relevant for detailed statistical analyses and cross-comparisons. Here, we present a pilot study on the application of 3D surface digital microscopy to quantify bone surface textures on the long \nbones of the grey heron (Ardea cinerea) and the Canada goose (Branta canadensis) using internationally verifed \nroughness parameters. Using a standardised measuring protocol, computed roughness values show a strong correlation with qualitative descriptions of textural patterns. Overall, higher roughness values correspond to increased numbers of grooves and pits and vice versa. Most of the roughness parameters allowed distinguishing between diferent \nontogenetic classes and closely followed the typical sigmoidal animal growth curve. Our results show that bone \ntexture quantifcation is a feasible approach to identifying ontogenetic age classes.
    Keywords: General Physics and Astronomy ; General Environmental Science ; General Biochemistry ; Genetics and Molecular Biology ; General Materials Science ; General Chemistry ; Roughness ; Surfaces ; Taphonomy ; Topography ; Bone ; Ontogeny ; Digital microscopy
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
    ISSN: 1871-4528
    Keywords: Klima ; Witterung ; Qualität ; Trockenheit ; Sorte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The effect of chitting and planting time of potato seed on the suitability of the crop for crisp production was investigated in a 5-year trial. The second-early table variety Bintje and the two early-main crisping varieties Maritta and Saturna were used. Three chitting periods (0, 6 and 12 weeks) and two planting dates (the beginning of April and May) were investigated. The change in crisping quality over a 7–8 month storage period was checked by frying tests at two to two-and-a-half monthly intervals. The criterion of quality was the colour of the crisps. Duration of chitting had little effect on crisping quality. The effect of planting date was strongly affected by the weather in a given year. In most years, but not for the experiment overall, the colour rating of the chips was slightly but significantly better for the later rather than the earlier planting date. The two crisping varieties Maritta and Saturna reached optimum suitability for crisping about twothirds of the way through the storage period, i.e. about March, the late plantings showing a more marked improvement in quality than the early ones (Table 1, Fig. 1–4). The weather, sometimes in combination with various soil conditions, had the greatest influence on the experimental results. This is concluded since the effects of the individual experimental factors depend on the season (Fig. 1–4) and from the difference in the averaged yearly results. Statistical analysis showed highly significant years and all experimental factors but chitting. 1976 merits special attention due to the extremely warm and dry summer weather. Potatoes which at the start of storage were generally poor showed a great improvement in quality during storage, especially those from the later planting. From the results it is obvious that the producer of quality potatoes for industry faces difficulties in choosing growing methods for improving quality due to the unpredictability of the consequences of weather conditions.
    Abstract: Résumé L'influence de la durée de prégermination des plants et de la date de plantation sur l'aptitude des pommes de terre à la fabrication de pommes chips a été examinée dans un essai répété pendant 5 ans. Les cultivars ci-après ont été examinées: Bintje, variété mi-précoce de consommation, Maritta et Saturna, variétés mi-tardives présentant une très bonne aptitude à la fabrication de pommes chips. Trois procédés de prégermination (0, 6 et 12 semaines) ainsi que deux dates de plantations (début avril et début mai) ont été comparés. L'évolution de la qualité des chips au cours d'une durée de conservation de 7 à 8 mois, a été contrôlée à intervalles de deux mois à deux mois et demi, par des tests de fabrication. La couleur des pommes chips a constitué le critère de qualité. La prégermination n'a pratiquement pas influencé la qualité des chips. L'effet de la date de plantation était en relation étroite avec les conditions météorologiques de l'année. Sur un grand nombre d'années d'essais et compte tenu des exceptions, une amélioration peu importante mais néanmoins significantive de la qualité des chips, a été obtenue par la plantation tardive, par rapport à la plantation précoce. Pour les variétés spécifiquement aptes à la fabrication de chips, Maritta et Saturna, les tubercules ont atteint leur qualité optimale aux deux tiers de la durée de conservation, soit en mars environ. L'amélioration de la qualité a été plus prononcée pour les tubercules issus de la plantation tardive que pour ceux de la plantation précoce (tableau 1, fig. 1–4). Ce sont les conditions de croissance et les différences de structure du sol qui ont influencé le plus les résultats de ces essais. L'effet de l'année sur les paramètres examinés a été évident (fig. 2–4). L'analyse statistique (tableau 1) donne une interaction hautement significative entre les années et les paramètres d'essais, exception faite de la prégermination. Les résultats de l'année 1976 méritent une attention particulière, en raison des températures élevées, de la sécheresse durant l'été. La qualité des tubercules a été plutôt médiocre en début de conservation. Par la suite, plusieurs lots, et particulièrement ceux de la plantation tardive, se sont fortement améliorés (fig. 3). Ces résultats démontrent pour la production de pommes de terre destinées à la transformation industrielle, les difficultés auxquelles se heurte le choix des techniques culturales appropriées, en raison des conditions météorologiques imprévisibles.
    Notes: Zusammenfassung Die in einem mehrjährigen Versuch (1973–1977) mit den Sorten Bintje, Maritta und Saturna geprüften Faktoren Vorkeimen und Pflanzzeitpunkt des Saatgutes sowie Lagerdauer des Erntegutes, übten folgende Einflüsse auf die Farbe von daraus hergestellten Pommes Chips aus: - Spätes Pflanzen (anfangs Mai) brachte in der Mehrzahl der Versuchsjahre eine leichte Verbesserung der Chipsfarbe bei jeweils mindestens zwei der drei Versuchssorten gegenüber frühem Pflanzen (anfangs April). - Die Vorkeimdauer hatte keinen Einfluss. - Mit zunehmender Lagerdauer trat mindestens bis zum Monat März bei den beiden Chips-Sorten Maritta und Saturna eine Qualitätsverbesserung ein, die bei den spätgepflanzten Varianten etwas deutlicher ausfiel als bei den frühgepflanzten. Die Ergebnisse wurden durch die Jahreswitterung und teils auch durch die Bodenbeschaffenheit stark beeinflusst.
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  • 3
    ISSN: 1434-193X
    Keywords: Photocycloaddition ; Ring opening ; Oxetanes ; 1,2-Diols ; Alkyldealkoxylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ring opening of 3-isopropyl-2-phenyl-3-oxetanol (2a) by various nucleophiles has been studied. In the presence of BF3 as a Lewis acid, a clean reaction at the less substituted C-4 position was observed and the corresponding 1,2-diols 6-11 and 21-23 were isolated in diastereomerically pure form (47-97% yield). Alkyl-, aryl-, alkynyl- and alkenyllithium compounds proved to be suitable carbon nucleophiles. Deprotonated thiols were used as sulfur nucleophiles. An alkoxide derived from benzyl alcohol and an amide derived from benzylamine reacted less readily under these conditions, yielding the 1,2,3-trifunctional compounds 24 (42% yield) and 26 (54% yield). Other 2-phenyl-3-oxetanols such as 2b and 2c can also be employed as electrophiles, whereas 2-anisyl derivatives preferentially undergo rearrangement reactions, as exemplified by the conversion of oxetane 16 to the hydroxy ketone 17 (84% yield). The superior behaviour of 3-oxetanols as compared to their silyl derivatives in reactions with nucleophiles became evident from the reaction of 3-silyloxyoxetane 1a with alkyllithium reagents. A β elimination occurred upon treatment with nBuLi, which, after pericyclic ring opening and addition of nBuLi, yielded the allylic alcohol 20.
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  • 4
    ISSN: 1434-193X
    Keywords: Azoalkanes ; DBO ; Fluorescence quenching ; Exciplexes ; Hydrogen transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fluorescence of the DBO derivatives 1-3 is efficiently quenched by olefins and arenes, exciplex formation and hydrogen transfer operate as quenching mechanisms. The electron-accepting ester groups in the azoalkanes 1-3 promote significantly more effective quenching compared to the parent DBO. Steric hindrance accounts for the differences in the quenching efficiencies, but electronic effects dominate
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  • 5
    ISSN: 1434-193X
    Keywords: Mannich bases ; γ-Amino alcohols ; Grob fragmentation ; (Z)-Alkenes ; Oxetanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quaternized γ-amino alcohols 5 derived from ternary iminium salts 2 are stereospecifically converted into both unsaturated aldehydes/ketones 6 with a (Z)-C—C double bond in a Grob-type fragmentation and highly functionalized oxetanes 7 by intramolecular substitution.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2201-2207 
    ISSN: 1434-193X
    Keywords: Antibiotics ; Asymmetric synthesis ; β-Lactams ; Michael additions ; Multicomponent reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium dialkylcuprates react either in a sequential one-pot or in a domino “three-component” fashion with chiral Michael acceptors, like Oppolzer's N-enoyl-2,10-camphorsultams 7 and 11 or ‘Evans’ N-enoyl-4-phenyl-1,3-oxazolidin-2-ones 8 and 13, and N-(methoxycarbonylmethylidene)(4-methoxyphenyl)amine 9 to afford the corresponding cis-3-alkyl-4-methoxycarbonyl-1-(4-methoxyphenyl)azetidin-2-ones 10, 14-15 in overall yields of 40-67% and enantiomeric excesses of 91-99%.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2229-2235 
    ISSN: 1434-193X
    Keywords: 3-Nitro-ω-benzylideneacetophenone ; Carbanions ; Michael addition ; Intramolecular vicarious nucleophilic substitution of hydrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Nitro-ω-benzylideneacetophenone (1) reacts with carbanions containing leaving groups to give addition products to the electrophilic side chain. As a result of conjugated addition and subsequent intramolecular vicarious nucleophilic substitution of hydrogen (VNS) in the nitroaromatic ring of 1 in the position para to the nitro group, 4-cyano-7-nitro-3-phenyl-1,2,3,4-tetrahydronaphthalen-1-one and 4-cyano-7-nitro-3-phenylnaphth-1-ol are obtained. Smooth intramolecular VNS in the position para to the nitro group was observed for 4-chloro-1-(3-nitrophenyl)-3-phenyl-4-(p-tosyl)butanol.
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  • 8
    ISSN: 1434-193X
    Keywords: Conformation analysis ; Electrochemistry ; Nitrogen heterocycles ; Dimerization ; Mechanism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In aqueous media the one-electron reduction of the title compounds on a mercury pool generally gives rise to three dimers, which are distinguishable by HPL chromatography. From spectroscopic analyses it has been possible to propose a structure for these conformers and their stability has been studied. Two conformers are unstable, yielding the third conformer. A mechanism is proposed for this transformation.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 837-846 
    ISSN: 1434-193X
    Keywords: AZT ; cycloSal-pro-nucleotide ; Prodrugs ; Nucleotide delivery ; HIV chemotherapy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of our cycloSaligenyl- (cycloSal) pronucleotide concept to the approved anti-HIV dideoxynucleoside 3′-azido-3′-deoxythymidine AZT (1) is reported. This pro-nucleotide concept has been designed to deliver the corresponding 3′-azido-3′-deoxythymidine monophosphate AZTMP (2) by selective chemical hydrolysis from the lipophilic precursors cycloSal-AZTMP 4a-h. All derivatives 4a-h were synthesized using differently substituted salicyl alcohols 7a-h as starting materials. In hydrolysis studies, compounds 4 decomposed selectively releasing AZTMP (2) and the salicyl alcohols 7 following the designed tandem reaction. Furthermore, due to the electronic properties introduced by substituents, the half-lives of the triesters 4 could be ajusted over a wide range. Phosphotriesters 4 exhibited considerable biological activity in HIV-1 and HIV-2 infected wild-type human T-lymphocyte (CEM/O) cells, whereas, contrary to our expectations, nearly all activity was lost in HIV-2 infected thymidine-kinase-deficient CEM cells.
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  • 10
    ISSN: 1434-193X
    Keywords: N-Alkylation ; Diketopiperazine building block ; Peptidomimetics ; RGD analogues ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a new scaffold for peptidomimetic synthesis, a highly constrained bifunctional diketopiperazine, 4, has been prepared by smooth N-alkylation with tert-butyl bromoacetate. As a first application, we describe herein the synthesis of new peptidomimetics of the Arg-Gly-Asp (RGD) sequence. The product 30, which shows a selective platelet-aggregation inhibiting activity, can be used as a lead for the preparation of more potent products.
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