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51.
W. M. TH. J. De Brouwer L. J. B. Cornelissen P. C. Van Zwet 《European journal of plant pathology / European Foundation for Plant Pathology》1974,80(2):75-76
Samenvatting Er wordt een apparaat beschreven om automatisch per uur bladluisvangsten te verrichten. De apparatuur bestaat uit 24 gele vangbakken, die ieder één uur per etmaal open staan. Onder de vangbak bevindt zich een Servo-motor, die op het gewenste tijdstip een deksel over de bak schuift of wegschuift (Fig. 1). De Servo-motor krijgt het commando daartoe van een programma-schakelaar (Fig. 2). 相似文献
52.
53.
Although ordinary chondrite (OC) meteorites dominate observed falls, the identification of near-Earth and main-belt asteroid sources has remained elusive. Telescopic measurements of 35 near-Earth asteroids ( approximately3 kilometers in diameter) revealed six that have visible wavelength spectra similar to laboratory spectra of OC meteorites. Near-Earth asteroids were found to have spectral properties that span the range between the previously separated domains of OC meteorites and the most common (S class) asteroids, suggesting a link. This range of spectral properties could arise through a diversity of mineralogies and regolith particle sizes, as well as through a time-dependent surface weathering process. 相似文献
54.
J. G. TH. Hermsen 《Euphytica》1957,6(1):18-25
Summary Seven of the wheat crosses which were performed in 1954 and 1955 produced a uniform semi-lethal F1. Among these were four combinations with the spring wheat Koga and two with the Turkish winter wheat Eskischir. The degree of withering in the F1 appeared to be dependent on the variety with which Koga or Eskischir were combined. In the F2 of the Koga crosses carried out in 1954 a 9 : 7 ratio of semi-lethals and normal plants was found. The almost continuous gradation in semi-lethality within the group of semi-lethal plants of every F2 was conspicuous.The facts are explained as follows: Two complementary genes determine the semi-lethality as such, while modifying genes are responsible for the different degrees of semi-lethality of the different F1's and for the variation in degree of semi-lethality within every F2. In the discussion this explanation is given in detail.It is pointed out that it is perhaps possible, with the aid of the phenomenon of semi-lethality, to discover or confirm relationships between species and/or varieties.Finally it is suggested that the rejection of F1's with withering symptoms is premature. 相似文献