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  • 1
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A new radiotracer method has been developed to measure the migration of trace elements from food contact packaging into four standard food simulants; acetic acid, ethanol, olive oil, deionised water. A sample of material is irradiated in a thermal neutron flux of 1016n·m−2·s−1 to activate the trace elements and produce a range of radionuclides. The sample is then placed in the food simulant and the migration of the radionuclides is monitored by performing γ-ray spectrometry on a sample of the simulant. Any radionuclides measured must be due entirely to the migration of the elements present in the plastic, since the simulant itself is not radioactive. Preliminary studies have shown that detection limits of around 0.2μg·dm−2 (0.002 mg/kg) can be achieved for antimony in a sample of polyethylene terephthalate. This method can now been extended to measure migration into real foods. This will highlight any differences between the standard simulants currently used and real foods. Since the method only involves irradiation of the packaging material, any food matrix can be studied.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-8248
    Keywords: Plodia interpunctella ; Venturia canescens ; Corcyra cephalonica ; defensive behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résmé Les intéractions, sur le plan comportemental, entre le parasitoïde solitaire koïnobionte,Venturia canescens et deux de ses hôtes,Plodia interpunctella etCorcyra cephalonica ont fait l'objet de cette étude. La réponse des deux hôtes à une exploration antennaire simulée à l'aide d'un pinceau à 2 poils différait selon qu'il s'agissait des petites larves du 3e stade ou des grosses larves du 5e stade. En réponse à ce stimulus, les jeunes larves deP. interpunctella adoptaient principalement un comportement de fuite (en se contorsionnant ou en se débattant) alors que les larves de 3e stade deC. cephalonica se montraient plus agressives (en rejetant la tête en arrière et en donnant des coups de patte). Au stade L5, les larves deP. interpunctella s'immobilisaient après l'application du stimulus, alors que celles deC. cephalonica avaient une réponse moins agressive qu'aux stades précédents. Alors queV. canescens enfoncait rapidement son ovipositeur dans les 2 hôtes après une exploration antennaire,P. interpunctella était nettement plus sensible à l'attaque du parasitoïde queC. cephalonica, et ce sans tenir compte de la taille du dernier stade (L5).C. cephalonica, l'hôte le plus grand et le plus agressif, résiste activement au parasitisme tandis quePlodia répond de façon beaucoup plus passive au contact du parasitoïde. Les parasitoïdes examinent les hôtes morts et y enfoncent leur ovipositeur, mais les attaques ne sont pas poursuivies et les femelles s'en désintéressent rapidement. Sur des sites oùV. canescens est en présence de larves du 5e stade deC. cephalonica on deP. interpunctella, la plupart des larves deP. interpunctella répondaient au contact avec le parasitoïde par l'immobilité, alors que les larves deC. cephalonica adoptaient une attitude un peu plus agressive. Les larves deP. interpunctella qui s'immobilisaient échappaient habituellement au parasitisme tandis que celles qui tentaient de fuir étaient poursuivies avec vigueur par le parasitoïde et généralement parasitées. En dépit de leur comportement après le contact,C. cephalonica évitait l'attaque avec plus de succès. L'acceptation de l'hôte parV. canescens est clairement dépendante de la taille et l'espèce de l'hôte qu'il attaque. Le rôle du comportement défensif de l'hôte est discuté en relation avec l'évolution de comportement de contre-défense du parasitoïde et de ses stratégies d'oviposition.
    Notes: Abstract Behavioural interactions between the solitary koinobiont parasitoid,Venturia canescens, and two of its hosts,Plodia interpunctella andCorcyra cephalonica, were investigated. The response of both hosts to simulated antennation using a two-haired brush was examined over instars 3 (L3) to 5 (L5). YoungP. interpunctella larvae predominantly adopted escape tactics (writhe, trash) whereas L5P. interpunctella usually froze after the stimulus was applied. L3C. cephalonica larvae were more aggressive (headrear, flick) thanP. interpunctella in response to the application of the stimulus, but olderC. cephalonica responded less aggressively than in earlier instars. AlthoughV. canescens readily jabbed its ovipositor at both hosts after antennation,P. interpunctella was considerably more susceptible to parasitoid attack thanC. cephalonica, irrespective of size in the final (L5) instar.C. cephalonica, the larger, more aggressive host, actively resisted parasitism whereasP. interpunctella responded much more passively after parasitoid contact. Parasitoids examined and jabbed their ovipositors at dead hosts, but this behaviour was not sustained, implying that host movement stimulates parasitoid attack. On patches containingV. canescens, L5C. cephalonica andP. interpunctella, mostP. interpunctella larvae responded by freezing after parasitoid contact.P. interpunctella that froze usually avoided parasitism, whereas larvae that attempted to escape by crawling were pursued with vigour byV. canescens and usually parasitized. Irrespective of behaviour after parasitoid contact,C. cephalonia displayed more aggressive behaviour and had much greater success in warding off parasitoid attack. Host acceptance byV. canescens is clearly affected by the size and species of the host it attacks. The influence of host defensive behaviour is discussed in relation to the evolution of parasitoid counter-defences and oviposition strategies.
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  • 3
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A neutron activation method has been developed for the analysis of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate and polystyrene. Samples weighing 2–5 g were irradiated in a thermal neutron flux of 1016 neutrons m−2 s−1 and measured with gamma ray spectrometry for 64 elements. With the method developed here over 50 elements can be detected at concentrations below 1 mg/kg. Correction factors were applied for neutron flux variation and counting geometry. The method was validated using reference material citrus leaves (NIST) for Na, Mg, Al, K, Ca, Mn, Cu, Sr and I, and a suite of ‘in house’ standards doped with Al, Cr, Co, Mg, Zn and Sb confirmed repeatability of the method. The method was used to measure inorganic contaminants in the raw polymers and retail samples of plastic packaging used in contact with food.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A neutron activation method has been developed for the analysis of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate and polystyrene food contact plastics. The method provides determination of over 50 elements at concentrations below 1 mg kg−1. This technique has now been extended to study migration from food contact materials into standard food simulants (olive oil, acetic acid, ethanol and water). Samples of plastic are irradiated in a thermal neutron flux to produce radionuclides of the elements present in the plastic. Over a period of time the radionuclides of these elements may travel from the plastic into the food simulants, and hence the migration can be determined. Gamma ray spectrometry is performed on the simulants at the end of the test to quantify the migration. Any activity present must be due only to the migration of radionuclides of elements in the plastic and nothing else. This eliminates the need for a blank determination, which is required with existing migration methods. Preliminary studies have shown that detection limits of around 0.002 mg kg−1 can be achieved for Sb in a retail polyethylene terephthalate (PET) bottle. This can be compared to levels of 0.005
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  • 5
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The use of paint as a coating for toys intended for sale on the European market is controlled by a European Standard (EN 71-3: 1994-European Standard for the Safety of Toys, Part 3—Migration of Elements). This work is the result of a preliminary study organised by the European Commission to produce a new paint reference material which can be used to validate the test methods given in the European Standard. The migration of elements from painted panels and comminuted paint produced by the Laboratory of the Government Chemist, (U.K.) was studied. Several methods were used in this certification exercise and this work reports the recults of neutron activation analysis and inductively coupled plasma mass spectrometry to determine the migration of As, Ba, Cd, Cr, Hg, Pb, Se and Sb into a simulated stomach environment. Replicate extracts obtained from paint samples gave a precision of within 10% for most elements by both analytical techniques for the paint panels and for the comminuted paint sample. This preliminary study has shown that the standard method can provide reproducible results for each of the paint materials studied and indicates that the study should be continued to produce a fully certified paint reference material.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have elaborated a procedure for numerically modelling the behaviour of polymer-based materials as a function of two independent variables such as temperature and rate. The parameters of the model are chosen to have close physical significance, e.g. in terms of molecular theories or other measurements. The model may be adjusted to the data by a least-squares fit, yielding the optimal parameters provided the chi-squared test shows the fit to be acceptably good. Specimens may be compared by studying the dependence of individual fitted model parameters on preparation variables. Under certain conditions this procedure can be extended to result in the quantitative prediction of the ingredients and preparation needed to produce a material of desired properties. We describe the implementation of the procedure on a computergraphics facility, and apply it to the study of the tear energy in filled vulcanizates.
    Type of Medium: Electronic Resource
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  • 9
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    London : Periodicals Archive Online (PAO)
    ISSN: 0305-7488
    Topics: Geography
    Description / Table of Contents: Other Studies
    Notes: Reviews
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  • 10
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    Chicago : Periodicals Archive Online (PAO)
    Agricultural History. 22:2 (1948:Apr.) 124 
    ISSN: 0002-1482
    Topics: History , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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