996 resultados para 20. Jahrhundert


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Effects of Basudine and Gammalin 20 on the fingerlings of Aphyosemin gairdneri were investigated using static bioassays and continuous aeration over a period of 48 hours. The 48 hours LC sub(50) of the exposed fish to Basudine and Gammalin 20 were determined to be 194.99 mu g dm super(3) and 95.50 mu g dm super(3) respectively. Gammalin 20 was more toxic than Basudine. The behavioural responses observed include agitation, erratic swimming, loss of equilibrium, period of quiescence and death. It is concluded that repeated applications of these herbicides should be avoided before stocking ponds with fish

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The impact of acute exposure of Gammalin 20 (an organochlorine pesticide) was investigated in a static bioassay test over a 96-(4-day) period on the fingerlings of Chrysichthys nigrodigitatus (lacepede). The 96-hLC sub(50) of Gammalin 20 was determined as 2.31 Ug/l with lower and upper limits of toxicities as 2.10 and 4.44 Ug/l respectively. At higher concentrations, the colour of the exposed fish became darker, opercular movement slowed down while pigmentation pattern increased and respiratory distress was observed, erratic swimming, tonic convulsion and no response to gentle prodding, and finally death. The implications of these results were discussed with a suggestion of the total ban on the use of Gammalin 20 in capture fisheries due to its harmful and persistence nature in the aquatic environment

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Based on the results of an analytical assessment, the Atlantic cod stock off Greenland collapsed already in the late 60s and, since then, reached rarely the 10 % level of its size in 1955. Applying the concept of a self-sustaining stock, the drastic harvesting strategy of the past four decades must be considered inadequate. The stock collapse was therefore found consistent with annual exploitation rates being not adjusted to conservative management options and exceeding the productivity of the stock by far. The results of a multiplicative model explained the following recruitment failure based on significant effects of spawning stock size as well as temperature. Certainly, cold periods have negatively affected the recruitment process and consequently contributed to the stock collapse. However, such ecological effects should not be itemized causal but must be taken into account regarding appropriate stock management. Till today, the spawning stock remained severely depleted causing a low probability of a successful recruitment and a substantial stock recovery.

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High-energy ion emission from intense-ultrashort (30fs) laser-pulse- cooled deuterium-cluster (80K) interaction is measured. The deuterium ions have an average energy 20keV, which greatly exceeds Zweiback's expectation [Phys. Rev. Lett. 84 (2000) 2634]. These fast deuterium ions can be used to drive fusion and have a broad prospect.

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Qualitative and quantitative characteristics of the reaction of certain fish to light were tested and reasons for the attraction of certain fish to light are discussed.

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The FIDAWOG workshop held at the Tom Mboya Labour College in Kisumu was the fourth stock assessment workshop held under the LVFRP programme. There were two main objectives: training in paper and report writing and presentation, and presentation of research results collected to date.

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The effectiveness of 17 α-hydroxy-20 β-dihydroprogesterone (17 α-20 β Pg) or of a trout hypophyseal gonadotrophic extract on the in vitro intrafollicular maturation of trout oocytes can be modulated by steroids which do not have a direct maturing effect; the effectiveness of the gonadotrophic extract is lowered by oestradiol and oestrone and increased by testosterone. As these steroids have no significant effect on maturation induced by 17 α-20 β Pg, the site of their activity is probably in the follicular envelopes. Corticosteroids, and Cortisol and cortisone in particular increase the effectiveness of the gonadotrophic extract, but increase the effectiveness of 17 α-20 β Pg even more strongly, suggesting that this 'progestagen' has a direct effect on oocyte sensitivity.

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The lowest T = 2 states have been identified and studied in the nuclei 12C, 12B, 20</sup>F and and 28Al. The first two of these were produced in the reactions 14C(p,t)12C and 14C (p,3He)12B, at 50.5 and 63.4 MeV incident proton energy respectively, at the Oak Ridge National Laboratory. The T = 2 states in 20</sup>F and 28Al were observed in (3He,p) reactions at 12-MeV incident energy, with the Caltech Tandem accelerator.

The results for the four nuclei studied are summarized below:

(1) 12C: the lowest T = 2 state was located at an excitation energy of 27595 ± 20 keV, and has a width less than 35 keV.

(2) 12B: the lowest T = 2 state was found at an excitation energy of 12710 ± 20 keV. The width was determined to be less than 54 keV and the spin and parity were confirmed to be 0+. A second 12B state (or doublet) was observed at an excitation energy of 14860 ± 30 keV with a width (if the group corresponds to a single state) of 226 ± 30 keV.

(3) 20</sup>F: the lowest T = 2 state was observed at an excitation of 6513 ± 5 keV; the spin and parity were confirmed to be 0+. A second state, tentatively identified as T = 2 from the level spacing, was located at 8210 ± 6 keV.

(4) 28Al: the lowest T = 2 state was identified at an excitation of 5997 ± 6 keV; the spin and parity were confirmed to be 0+. A second state at an excitation energy of 7491 ± 11 keV is tentatively identified as T = 2, with a corresponding (tentative) spin and parity assignment Jπ = 2+.

The results of the present work and the other known masses of T = 2 states and nuclei for 8 ≤ A ≤ 28 are summarized, and massequation coefficients have been extracted for these multiplets. These coefficients were compared with those from T = 1 multiplets, and then used to predict the mass and stability of each of the unobserved members of the T = 2 multiplets.

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Laboratory research was done in order to study the feeding of larval Cricotopus silvestris F. in relation to characters of structure of oral apparatus. Results of the experiments are summarised and the oral apparatus morhologically described.

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The morphology, increase and systematica of Sphaerotilus natans is studied and culture methods examined.

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Sampling was concentrated on the North Moor region and the series of ditches which drained this area to the Bristol Channel. Although most ditches were not deep the mud substratum precluded sampling from within the habitat. All samples were taken with a pond net from the banks. Efforts were made to sample each part of the habitat although in some ditches the macrophyte growth was so intense as to make sampling difficult particularly of the sediments. Organisms were identified on the 10 sampling sites.

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Este primer Congreso Interuniversitario sobre el Trabajo Fin de Grado ha supuesto un encuentro y un espacio de reflexión e intercambio de diversas experiencias procedentes de los distintos grados y áreas de conocimiento de las universidades participantes. Esta diversidad se ha manifestado en las temáticas presentadas, que hacen referencia a: normativas de TFG, modalidades de TFG, número de créditos y del peso académico del TFG en cada plan de estudios, enfoques e instrumentos de evaluación, desarrollo de materiales para la elaboración del TFG, guías docentes, defensas del TFG, las plataformas de gestión integral desarrolladas en algunas universidades, etc. También se ha reflexionado sobre las diversas formas de la difusión de los TFG (Open Access, repositorios digitales propios de cada universidad) y la transferencia de conocimiento desde los grados a los distintos sectores de la sociedad, la cultura, economía, tecnología, salud, innovación social, etc.