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  • 1
    Keywords: Electronics ; Materials ; Nanotechnology
    ISBN: 9783540328209
    Language: English
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  • 2
    ISSN: 0016-7835
    Keywords: Key words Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Potato research 3 (1960), S. 47-79 
    ISSN: 1871-4528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 4
    ISSN: 1871-4528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The influence of high (80–100% WHC) and low (20–30% WHC) soil moisture during different growth stages on growth and development of the early varietyBarima was investigated by means of pot experiments under controlled temperature (for treatments see Table 1). Constant high soil moisture (Treatment 1), as compared with low soil moisture (Treatment 2), increased the growth rate of stems (Fig. 1), leaf area (Fig. 2) and tubers (Fig. 3). The net assimilation rate (Table 2) was higher and the number of tubers (Fig. 4) greater but, in contrast to low soil moisture conditions, about 50% of the tubers was resorbed during succeeding periods of growth. Plants flowered earlier and more abundantly and the length of the growing period was shorter. Low soil moisture during the early growth stages only (Treatments 3–6) increased productivity of the plants, partly by lengthening the period of high growth rate and partly by increasing rates of growth and net assimilation (Fig. 1–3, Table 2). Highest tuber yields occurred where there had been an initial dry period of up to 36 days. Low soil moisture following a period of high soil moisture (Treatments 7–9) caused a pronounced reduction in the growth rates of aerial organs (Fig. 1–3) followed by shedding of the basal leaves. The growth rate of the tubers was reduced to a lesser extent and resorption of tubers decreased. High soil moisture prior to tuber set increased tuber initiation during the subsequent dry period (Fig. 4). Water consumption was doubled at high soil moisture. Soil moisture during the growth of the mother plants influenced the seed value of the tubers (Table 3). Initial dry periods decreased time to emergence and increased growth in height of the young plants. The influence of changing soil moisture conditions on growth and bulking in the field are discussed.
    Abstract: Résumé Les auteurs ont recherché l’influence d’une humidité du sol élevée (80–100% de la capacité de saturation c.s.) et basse (20–30% c.s.) sur la croissance et le développement de la variétéBarima au cours de divers stades de végétation; les essais furent réalisés en vases de végétation et sous température contrôlée (voir tableau 1, traitements). Comparativement à une basse teneur constante (traitement 2), une teneur élevée constante d’humidité du sol (traitement 1) augmente les taux de croissance des tiges (fig. 1), de la surface foliaire (fig. 2) et des tubercules (fig. 3). De même, sont plus importants les taux d’assimilation nette ainsi que le nombre de tubercules (fig. 4), mais, contrairement à ce qui se passe dans des conditions de basse teneur en humidité du sol, quelque 50% des tubercules sont résorbés pendant la période suivante de croissance. Les plantes fleurissent plus tôt et plus abondamment. La période de végétation est plus courte. La basse teneur en humidité du sol, pendant seulement la première période de croissance (traitements 3–6), augmente la productivité des plantes grâce à un allongement de la période de taux de croissance et partiellement grâce à des taux de croissance plus élevés et par un taux plus élevé de l’assimilation nette (fig. 1–3, tableau 2). On onserve les productions de tubercules les plus élevées après une période initiale de sécheresse jusqu’à 30 jours (fig. 3). Une basse teneur en humidité du sol succédant à une période d’humidité élevée (traitements 7–9) provoque une importante réduction des taux de croissance des organes aériens (fig. 1–3) et, conséquemment, la chute des feuilles du bas. Les taux de croissance des tubercules sont peu réduits et la résorption des tubercules déjà constitués est diminuée. Une haute humidité du sol avant la formation des tubercules augmente l’initiation de ceux-ci pendant les périodes sèches suivantes (fig. 4). La consommation de l’eau était doublée lors d’une haute teneur en humidité du sol. L’humidité du sol pendant la croissance des plantes maternelles influence la valeur ‘plant’ des tubercules (tableau 3). Des périodes de sécheresse initiales réduisent la durée de levée et accélère l’allongement des tiges des jeunes plantes. Les auteurs discutent de l’influence des conditions d’humidité du sol sur la végétation et la productivité au champ.
    Notes: Zusammenfassung In Modellversuchen wurde der Einfluss hoher und niedriger Bodenfeuchte während verschiedener Wachstumsabschnitte auf Wachstum und Ertragsbildung der KartoffelsorteBarima untersucht. Hohe Bodenfeuchte in Vergleich zu konstant niedriger Bodenfeuchte förderte Entwicklung und Wachstum während der ersten Wachstumsabschnitte, die Vegetationsdauer war jedoch kürzer und ein hoher Anteil der angelegten Knollen wurde wieder resorbiert. Trockenheit während der Anfangsentwicklung, gefolgt von hoher Bodenfeuchte, förderte Wachstum und Ertragsleistung stärker als konstant hohe Bodenfeuchte. Trockenheit nach anfangs hoher Bodenfeuchte führte hingegen zu einer Reduktion der Wachstumsraten, besonders bei den oberirdischen Organen.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Potato research 5 (1962), S. 93-122 
    ISSN: 1871-4528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The object of the article is to present a survey of the present state of our seed potato research. An examination was made into the influence of certain growth factors on the development and metabolism of potato plants under controlled climatic conditions. The aim of this work is to help us to provide the basis of a directed method of influencing development, thereby permitting a better interpretation of the field trials. The main emphasis of our work was on the temperature and atmospheric humidity during storage, the soil temperature after planting out, as well as the atmospheric temperature and light conditions during the growth of the unripe plants. Attention was given both to the direct effect on the plant of the above factors and their “after-effect” during the subsequent course of development. In the field trial the effect of the weather and management was studied in connection with storage and the preparation of seed material. In this case we were mainly concerned with problems of fertilisation, plant spacing, planting depth, weed control, harvest date with reference to seed material, and also the grading and storage of the latter. Metabolism and physiology studies were made in connection with these problems. The article not only provides a survey but lists the main problems of our future research work.
    Abstract: Résumé L’article vise à donner un aperçu de l’état actuel de nos recherches relatives aux plants de pomme de terre. L’influence de certains facteurs de croissance sur le développement et le métabolisme de la plante de pomme de terre a été étudiée dans des conditions climatiques contrôlées. Ces travaux doivent contribuer à fournir la base d’une méthode permettant d’influer systématiquement sur le développement, afin de pouvoir interpréter mieux les essais effectués en plein champ. La température et l’humidité de l’air durant la période de stockage, la température du sol après la plantation, ainsi que la température de l’air et les conditions d’éclairage pendant la croissance des plantes vertes ont fait l’objet principal de notre étude. Outre l’influence directe exercée sur les plantes par les facteurs précités, nous avons observé leur “effet ultérieur”, c’est-à-dire leur influence sur l’évolution ultérieure de la plante. Dans les essais en plein champ, l’influence des conditions météorologiques et des mesures culturales a été étudiée en rapport avec le stockage et la préparation des plants. lci. les principaux problèmes étaient ceux de la fumure, de l’espacement des plantes, de la profondeur de plantation. de la lutte contre les mauvaises herbes et du moment de la récolte pour l’obtention de plants, ainsi que le triage et le stockage de ces derniers. Ces problèmes ont été étudiés en rapport avec des recherches physiologiques sur le métabolisme. Les exposés donnent non seulement une vue d’ensemble, mais aussi une indication des points principaux pour la continuation de nos recherches.
    Notes: Zusammenfassung Der Beitrag soll einen Überblick über den Stand unserer Forschung am Kartoffelpflanzgut vermitteln. Unter kontrollierten Klimabedingungen wurde der Einfluß bestimmter Wachstumsfaktoren auf die Entwicklung und den Stoffwechsel der Kartoffelpflanze untersucht. Diese Arbeiten sollen uns helfen, die Grundlage für eine gezielte Entwicklungsbeeinflussung zu schaffen, um somit die Feldversuche besser interpretieren zu können. Die Temperatur und Luftfeuchtigkeit während der Lagerung, die Bodentemperatur nach dem Auspflanzen, sowie die Lufttemperatur und die Lichtbedingungen während des Wachstums der grünen Pflanze standen im Vordergrund unserer Arbeit. Neben der unmittelbaren Beeinflussung der Pflanze durch die vorgenannten Faktoren wurde auch deren “Nachwirkung” im weiteren Entwicklungsverlauf Beachtung geschenkt. Im Feldversuch wurde in Verbindung mit der Lagerung und Pflanzgutvorbereitung der Einfluß von Witterung und Kulturmaßnahmen untersucht. Hier interessierten vorwiegend Problemen der Düngung, des Standraumes, der Pflanztiefe, der Unkrautbekämpfung, des Erntetermins im Hinblick auf Pflanzgut, sowie seine Sortierung und Lagerung. Im Zusammenhang mit diesen Fragen standen stoffwechselphysiologische Untersuchungen. Neben der Zusammenschau sollen die Ausführungen auch die Schwerpunkte unserer weiteren Forschungsarbeit aufzeigen.
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  • 6
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract There is increasing concern about the degradation and metabolisation as well as the biochemical mechanisms of action of organometallic compounds. They are known to be immunotoxic and/or neurotoxic. Because of their different toxic capacities, the development of a reliable correlation between molecular parameters and biochemical effects, which could be helpful in risk assessment, was an aim of this study. The tested organolead and -tin compounds decrease the viability of human cells in culture in a time- and concentration-dependent manner. Parabolic QSAR1 1 The abbreviations used are: TMT, trimethyltin chloride; TET, triethyltin bromide; TPT, tripropyltin chloride; TBT, tri-n-butyltin chloride; DBT, di-n-butyltin dichloride; TEL, triethyllead chloride; DEL, diethyllead dichloride; TML, trimethyllead chloride; TPhL, triphenyllead chloride; QSAR, quantitative structure-activity relationships; TSA, total surface area; MWion, ionic molecular weight; fMLP, N-formyl-L-methionyl-L-leucyl-L-phenylalanine; fluo-3, fluo-3 free acid; fluo-3 AM, fluo-3 acetoxymethyl ester; Me2SO, dimethyl sulfoxide; PLA2, phospholipase A2 (EC 3.1.1.4); FCS, fetal calf serum; HEPES, 4-(2-hydroxy-ethyl)-1-piperazineethanesulfonic acid; EGTA, [ethylene-bis(oxyethylenenitrilo)]tetraacetic acid; [Ca2+]i, cytosolic free Ca2+ concentration models yield an adequate correlation between toxicity expressed as LC50 and structural parameters like ionic molecular weight (MWion) or total surface area (TSA). Two main chemical attributes of the organometals are probably responsible for such a parabolic relationship: the hydrophobic side chain and the polar metal atom. Furthermore, all tested organometal compounds evoke a persistent increase of the cytosolic free calcium concentration [Ca2+]i. This effect is mainly due to an influx from the extracellular space. Further results suggest that Ca2+ enters the cell via opened calcium channels. Based on the essential role of Ca2+ within cellular signalling, the perturbation of calcium homeostasis appears to be an important event in final cell killing by organometals and it is most likely that other biochemical mechanisms, e.g. activation of phospholipase A2, are possibly mediated by an increase of [Ca2+]i.
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  • 9
    ISSN: 1573-4846
    Keywords: SAXS ; TEM ; nanocomposites ; hybrid materials ; surface modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were used to characterize the morphology of thermoplastic nanocomposites. These materials were based on a thermoplastic matrix of a copolymer of methylmethacrylate (MMA) and 2-hydroxyethylmethacrylate (HEMA) with spherical 10 nm silica particles as a filler (filler content 2, 5 and 10 vol%, respectively). Depending on the surface modification of the particles, it was possible to control the aggregation tendency of the primary filler particles. With uncoated particles large aggregates about 100 nm in size could be observed by TEM. For nanocomposites containing particles coated with methacryloxypropyltrimethoxysilane (MPTS), TEM showed that the particles were better dispersed in the polymer matrix only forming aggregates comprised of two or three primary particles. In comparison to the TEM results, the volume weighted particle size distribution calculated from SAXS for the systems with uncoated particles is monomodal and shows particle sizes in the range of primary particles whereas the systems with MPTS coated particles revealed a bimodal size distribution with particle sizes comparable to those measured with TEM. To obtain complete information about the morphology of the nanocomposites above the critical upper limit of detectable scattering vectors (particle sizes 〉50 nm) SAXS has to be supported by TEM, whereas in the nanosize range below the critical limit both methods exhibit an excellent correspondence.
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  • 10
    ISSN: 1573-4846
    Keywords: electrochromism ; sol-gel ; tungsten oxide ; peroxotungstic acid ; nanocrystalline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Stable tungsten oxide coating sols suitable for electrochromic applications were prepared by a modified peroxotungstic acid route. Layers up to 250 nm thickness could be deposited on ITO-coated and/or FTO-coated glass substrates in a single dip-coating process. Optoelectrochemical measurements were employed to determine the variation of the electrochromic properties (change in optical density (ΔOD) and switching times) of WO3-layers, investigated as a function of coating parameters, such as chamber humidity and the temperature of heat treatment. High resolution transmission electron microscopy (HR-TEM) has shown that the optimized layers possess a partially crystalline morphology with nanocrystalline regions 2–3 nm in size.
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