The toxicity of four insecticides and a herbicide under tropical conditions

The toxicities of four insecticides and a herbicide to Tilapia macrochir were tested in the laboratory. The 24 hour LC50's were estimated as follows: Endrin 20% ,0.008 ppm; Lindane 5% granules, 4.6 ppmm; Synexa 50 (HCH) 50%), 5.6 ppm; Synex 25 (HCH 25%), 14.8 ppm; TOK herbicide (Nitrofen), 100% survival for 24 hours at 100 ppm. These estimates agree with results obtained by other workers elsewhere in the world. The laboratory determination of toxicity is important in estimating the direct effects of poisonous substances on fish, but other indirect effects may result from their use. These should be investigated in the field

A description of certain indigenous fishing methods from Southern Dahomey

A survey of certain Dahomean fishing methods showed them to be specifically adapted to the exploitation of floodplains and shallow water lagoons. Several types of fish-parks are described, ranging from small installations thaI funclion as refuge traps, to larger constructions that act as a form of fish culture. Ponds are also dug in the floodplains in order to conserve fish isolated during the dry season. These methods all give high yields and are worthy of consideration for use elsewhere on the African continent

Studies on enclosed lagoons in the Jinja area

A number of lagoons have been studied in the Jinja region and a visit has been made to waters in Mwanza. Observations from aircraft have shown lagoons to be widely distributed at least throughout the northern and eastern shores of the lake, and because sand and rocky shores have remained relatively unaltered by the rising water level it seems possible that the flooding of swampy shores to form lagoons has been the principal environmental change due to rising water level

Hermann Paul et le concept d' analogie

This article discusses in detail the development of the concept of analogy by Hermann Paul, considered as the first theoretician in historical linguistics. First, the theorization of analogy by the Neogrammarians is analyzed, so as to highlight Paul’s originality. Secondly, the definition of analogy and its place in Paul’s Prinzipien der Sprachgeschichte are further developed. The most important observations are then resumed in a general conclusion.Cet article examine en détail le développement du concept d’analogie par Hermann Paul, qui est considéré comme le premier théoricien en linguistique historique. En premier lieu, nous étudions la théorisation de l’analogie par les néogrammairiens, afin de mieux cadrer l’originalité des concepts de Paul. Ensuite, nous développons la définition de l’analogie ainsi que la place occupée par ce concept dans les Prinzipien der Sprachgeschichte. Une conclusion générale reprend nos principales observations

Les marqueus cadratifs et argumentatifs dans les récits d'apprenants néerladophones du française L2. Premiers résultats d'une étude sur corpus

This article discusses the presence and frequency of use of framing and argumentative markers in narratives of Dutch learners of French in Brussels and Flanders. These learners are either at the beginning (1st year) or end (6th year) of their secondary school education. First, we provide with an overview of the notions that are analysed in the corpus. Next we describe the corpus and the task used, and then continue with a discussion of the results of the quantitative and qualitative analyses. To conclude, we sum up the main findings of our study.Cet article examine la présence et la fréquence de marqueurs cadratifs et argumentatifs présents dans les récits d'apprenants néerlandophones du français, dans deux contextes différents (en Flandre et à Bruxelles) et au début (1ère année de l'enseignement secondaire) et à la fin (6e année) de leur apprentissage du français. Nous commençons par un rappel des notions théoriques que nous opérationnalisons dans l'article, afin d'expliciter notre démarche. Nous détaillerons ensuite le corpus et la tâche utilisés, pour ensuite passer aux résultats des analyses quantitatives et qualitatives. Une conclusion générale reprendra nos principales observations

Blue harvest: inland fisheries as an ecosystem service

Global food production has increased greatly in recent years and rural livelihoods are much improved in many regions. Yet, despite this clear progress rural poverty and food insecurity remain deeply entrenched in many areas, especially in South Asia and sub-Saharan Africa. In response the international community has renewed calls for increased commitment to meeting the needs of the world's poor. This report, commissioned as a contribution to the 10th Conference of the Parties to the Convention on Biological Diversity taking place in Nagoya, Japan, not only underlines the value of freshwater fisheries but provides guidance on how the ecosystem approach can be applied in order to sustain future harvests.Inland fisheries, Nutrition, Food security, Sustainability, Ecosystems

A formal design synthesis and optimization method for systems architectures

International audienc

Tracking pupil mobility over the pre-school and primary school period: evidence from EPPE 3-11

This report describes the ‘tracking’ of the EPPE 3-11 sample and then goes on to examine the possible influence of mobility on EPPE 3-11 children’s cognitive progress and social/behavioural development over both the pre-school and primary school period. In the present research ‘mobility’ is defined as having changed pre-school or school centre at least once. The aims of the research are: • To determine possible means of reducing attrition in a longitudinal sample - tracking • To identify any likely predictors of mobility, that is, whether mobile individuals share any defining characteristics; • To investigate the effects of mobility when predicting children’s cognitive and social/behavioural outcomes, controlling for other background factors; • To investigate the effects of children’s mobility in terms of the academic effectiveness of the schools attended and to which children moved

Sailing towards the stars close to the speed of light

The authors describe the general motion of radiation-pushed sails accelerated near the speed of light with directed energy propulsion. Practical applications of the model are also given, including the interstellar flyby mission to the Alpha Centauri star system envisioned by the Breakthrough Starshot program. Any misalignment between the driving light beam and the direction of the sail's motion is naturally swept away during acceleration toward relativistic speed, yet leads to a deviation of about 80 A.U. in the case of an initial misalignment of 1 arc sec for a sail accelerated up to 0.2c toward Alpha Centauri. Then, the huge proper acceleration felt by the probes (of order 2500 g), the tremendous energy cost (of about 13 kt per probe) for poor efficiency (of about 3 \%), the trip duration (between 22 and 33 years), the temperature at thermodynamic equilibrium (about 1500 K), and the time dilation aboard (about 160-days difference) are all presented and their variation with the sail's reflectivity is discussed. We also present an application to single trips within the Solar System using double-stage light sails. A spaceship of mass 24 tons can start from Earth and stop at Mars in about seven months with a peak velocity of 30 km/s but at the price of a huge energy cost of about $5.3\times 10^4$ GWh due to extremely low efficiency of the directed energy system, around $10^{-4}$ in this low-velocity case.Comment: 15 pages, 10 figures, constructive comments welcome. Open Access Published version in Physical Review Research (5 nov. 2020