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Search Results: 1 - 10 of 352377 matches for " De Clercq D "
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Application of the Solid-Phase Julia–Lythgoe Olefination in Vitamin D Side-Chain Construction
Jo N. D'herde,Pierre J. De Clercq
Molecules , 2006, DOI: 10.3390/11080655
Abstract: An example of the Julia–Lythgoe attachment of the vitamin D side chain to a solid-phase linked Inhoffen–Lythgoe diol derived CD-ring fragment is reported.
Nymphal development and feeding preference of Podisus maculiventris (Heteroptera: Pentatomidae) on eggs of Ephestia kuehniella (Lepidoptera: Pyralidae) parasitised or not by Trichogramma brassicae (Hymenoptera: Trichogrammatidae)
Oliveira, H. N.;De Clercq, P.;Zanuncio, J. C.;Pratissoli, D.;Pedruzzi, E. P.;
Brazilian Journal of Biology , 2004, DOI: 10.1590/S1519-69842004000300009
Abstract: predation by podisus maculiventris nymphs, a predatory pentatomid, was evaluated with eggs of the flour moth ephestia kuehniella (pyralidae), parasitised or not by trichogramma brassicae (pupae stage). eggs of this pyralid were glued on rectangular cardboard and presented to nymphs of p. maculiventris as food. the pentatomid successfully reached adult stage when feeding on unparasitised eggs, indicating that flour moth eggs can be used as a factitious food for rearing this predator. pentatomid nymphs that received only parasitised eggs died before reaching fourth instar. in choice tests, p. maculiventris showed a preference for preying on unparasitised eggs of e. kuehniella rather than those containing pupae of t. brassicae. these results show that it is possible to combine the use of p. maculiventris with releases of t. brassicae in control programs of lepidopteran pests.
Studies on the biology of schistosomiasis with emphasis on the Senegal river basin
Southgate VR,Tchuem Tchuenté L-A,Sène M,De Clercq D
Memórias do Instituto Oswaldo Cruz , 2001,
Abstract: The construction of the Diama dam on the Senegal river, the Manantali dam on the Bafing river, Mali and the ensuing ecological changes have led to a massive outbreak of Schistosoma mansoni in Northern Senegal, associated with high intensity of infections, due to intense transmission, and the creation of new foci of S. haematobium. Data on the vectorial capacity of Biomphalaria pfeifferi from Ndombo, near Richard Toll, Senegal are presented with sympatric and allopatric (Cameroon) S. mansoni. Comparisons are made on infectivity, cercarial production, chronobiology of cercarial emergence and longevity of infected snails. Recent data on the intermediate host specificity of different isolates of S. haematobium from the Lower and Middle Valley of the Senegal river basin (SRB) demonstrate the existence of at least two strains of S. haematobium. The role of Bulinus truncatus in the transmission of S. haematobium in the Lower and Middle Valleys of the SRB is reviewed. Both S. haematobium and S. mansoni are transmitted in the same foci in some areas of the SRB.
Quantum engineering of atomic phase-shifts in optical clocks
T. Zanon-Willette,S. Almonacil,E. de Clercq,A. D. Ludlow,E. Arimondo
Physics , 2014, DOI: 10.1103/PhysRevA.90.053427
Abstract: Quantum engineering of time-separated Raman laser pulses in three-level systems is presented to produce an ultra-narrow optical transition in bosonic alkali-earth clocks free from light shifts and with a significantly reduced sensitivity to laser parameter fluctuations. Based on a quantum artificial complex-wave-function analytical model, and supported by a full density matrix simulation including a possible residual effect of spontaneous emission from the intermediate state, atomic phase-shifts associated to Ramsey and Hyper-Ramsey two-photon spectroscopy in optical clocks are derived. Various common-mode Raman frequency detunings are found where the frequency shifts from off-resonant states are canceled, while strongly reducing their uncertainties at the 10$^{-18}$ level of accuracy.
Historical Perspectives in the Development of Antiviral Agents Against Poxviruses
Erik De Clercq
Viruses , 2010, DOI: 10.3390/v2061322
Abstract: The poxvirus vaccinia virus (VV) served as the model virus for which the first antivirals, the thiosemicarbazones, were identified. This dates back to 1950; and, although there is at present no single antiviral drug specifically licensed for the chemotherapy or -prophylaxis of poxvirus infections, numerous candidate compounds have been described over the past 50 years. These compounds include interferon and inducers thereof (i.e., polyacrylic acid), 5-substituted 2’-deoxyuridines (i.e., idoxuridine), IMP dehydrogenase inhibitors, S-adenosylhomocysteine hydrolase inhibitors, acyclic nucleoside phosphonates (such as cidofovir) and alkoxyalkyl prodrugs thereof (such as CMX001), viral egress inhibitors (such as tecovirimat), and cellular kinase inhibitors (such as imatinib).
Dark clouds and their silver linings: exotic generalist predators in augmentative biological control
Neotropical Entomology , 2002, DOI: 10.1590/S1519-566X2002000200001
Abstract: several polyphagous arthropod predators are commercially available for augmentative biological control targeting mite and insect pests in a variety of cropping systems. a number of these predators are not native to the area of release. the current paper discusses benefits and risks of using exotic generalist predators as biocontrol agents. the fact that polyphagous predators are easily reared on unnatural foods and can be used against different pest species makes them attractive for commercialization. polyphagous or facultatively phytophagous predators have less difficulty in maintaining their populations at low prey densities and can sometimes be introduced in the crop before the target pest is present, thus preventing the buildup of pest populations before economic damage is done. on the other hand, generalists may interfere with the action of other beneficials in the crop, and facultative plant feeding by predatory arthropods exceptionally causes crop damage. the use of non-native natural enemies may entail environmental risks. in a growing number of countries, risk assessment procedures are being implemented that are largely focused on host range testing. it is emphasized, however, that the experimental evaluation of host specificity should be done under realistic conditions. furthermore, climatic matching and dispersal ability of an imported predator and the presence of its natural enemies in the area of introduction are important factors to be considered when assessing environmental risks. regulation is essential but should not hamper the implementation of biological control as an alternative to chemical pest control.
In de schaduw van ’s Gravesande. Het Leids Physisch Kabinet in de tweede helft van de 18e eeuw
Peter de Clercq
Tijdschrift voor de Geschiedenis der Geneeskunde, Natuurwetenschappen, Wiskunde en Techniek , 1987,
Abstract: Under's Gravesande's shadow. The Leiden Physical Cabinet in the second half of the 18th century. During the later 17th and the first half of the 18th century, the university of Leiden became an important center for the propagation of the experimental method in natural philosophy, especially through the Newtonian professor of physics W.J. 's Gravesande. Through the acquisition, after his death in 1742, of his private collection of instruments, Leiden became arguably the best equipped university on the continent for the teaching of experimental physics. Drawing mainly on unexplored financial documents in the university archives, this paper traces the rather less heroic era, which followed that highlight period in the history of the Leiden Physical Cabinet. Concentrating on the years 1742 to 1811, it demonstrates that the cabinet by no means fossilized, but doubled in size through the acquisition both of new (table 1) and 'second-hand' (table 2) instruments by's Gravesande's successors. These were, respectively, P. van Musschenbroek, J.N.S. Allamand, C.H. Damen and S. Speyert van der Eyk, each of whom tried to keep the cabinet in step with new developments in the field. Many of the 18th-century instruments from the Leiden Physical Cabinet are on permanent loan in the National Museum for the History of Science and Medicine, Museum Boerhaave, in Leiden, and this provides an extra stimulus to explore its growth and vicissitudes during the post-'s Gravesande period. A catalogue of this collection was published by C.A. Crommelin in 1926; a revised English edition followed in 1951. As argued in this paper, there are reasons for compiling a new catalogue, but there are problems of identification, and these are also discussed.
Instrumenten en universitaire laboratoria, ca. 1860-1940
Peter de Clercq
Tijdschrift voor de Geschiedenis der Geneeskunde, Natuurwetenschappen, Wiskunde en Techniek , 1986,
Abstract: Instruments and university laboratories, ca. 1860-1940. Both for research and teaching purposes, laboratories had to be equipped with scientific instruments. Focussing on university laboratories, this paper examines how this demand was met in the Netherlands during the period under review. Analysis of disused laboratory apparatus, now in the Museum Boerhaave collections, indicates that the bulk came from foreign, especially German firms. Rather than competing in producing them, Dutch entrepreneurs originally concentrated on importing and distributing these instruments. Thus trading firms specializing in furnishing laboratory equipment were established by Kipp (1829), Marius (1866), Salm (1898) and Lameris (1907). Their illustrated trade catalogues show the range of products available to laboratories. In the 1930’s there appear to have been too many sellers on the market, and this led to amalgamations. Meanwhile, various trading firms had successfully widened their activities, producing instruments often designed by Dutch researchers. As university laboratories grew in size and number, so did the number of instrumentmakers in their employ. As a result, apart from acquiring their instruments from outside, university laboratories often had apparatus designed and built on the spot. While there was an element of competition here, this development equally had beneficial effects on the instrument-making trade as a whole. Thus around 1900 a training institute for instrumentmakers was founded at the Physical Laboratory of Leiden University, an initiative copied in the Netherlands East Indies in 1920.
Antiviral Metal Complexes
Erik De Clercq
Metal-Based Drugs , 1997, DOI: 10.1155/mbd.1997.173
Towards an Ontology of Corporeal Uniqueness
Eva De Clercq
Skepsi , 2012,
Abstract: Pain, exhaustion, illness, infirmity, racism and sexism are all situations in which the body loses its daily familiarity. It would appear that not every experience is a daily lived experience (Erlebnis) or, as phenomenology puts it, an experience of meaning. The stress is not always on the lived immediacy of a centred subject. Experience can also provoke a loss of identity. Such a non-phenomenological account of experience can be found in Foucault’s notion of limit-experience, by which he means an experience that tears the subject from itself in such a way that it may arrive at dissociation. It has been suggested, for example by Drew Leder in The Absent Body, that experiences of dissociation encourage Cartesian dualism because they often result in an apparent cleavage of the self and the body. The article challenges this Cartesian mode of thinking through a brief discussion of John Maxwell Coetzee’s novel Elizabeth Costello, in particular Lessons Three and Four, ‘The Lives of Animals’, because this work reveals something crucial about the complexity of human embodiment. Coetzee’s lectures seem to suggest that we are wounded animals, not — or at least not solely — because of our physical vulnerability but because animality is no true option for us. The singularity of human existence distinguishes itself from the species character of animal life and this uniqueness has something to do with our body. The notion of corporeal vulnerability is usually understood in a relational sense, but it can also be something very intimate. This means that we are not only vulnerable in our bodily uniqueness, in the sense that our body is exposed to violence and death, but that we are also vulnerable to our bodily uniqueness, that is, exposed to it.
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