Imprints of the Little Ice Age and the severe earthquake of AD 2001 on the aquatic ecosystem of a tropical maar lake in El Salvador

Using a 530-year sediment record from the maar Lake Apastepeque, El Salvador, and based on diverse geochemical and biological (cladocerans, chironomids, diatoms, ostracods, testate amoebae) indicators, we estimated climatic and environmental alterations during the Little Ice Age (LIA) and reconstructed the recent history of the lake. Results demonstrate relatively humid conditions in the mid-elevations (500 m a.s.l.) of El Salvador during most parts of the LIA, resulting in high lake levels. Contrarily, the first part of the LIA was characterized by drier climates comparable to studies from Mexico and Belize, which correlated this phase with the Spörer minimum. Regional comparison with palaeorecords from the northern Neotropics reveals a high heterogeneity in local expressions of the LIA in Central America, likely connected to the high topographic heterogeneity of the region. Since the beginning of the 20th century, Lake Apastepeque has experienced enhanced human impact expressed as increased nutrient supply. The most recent period was characterized by significant environmental disturbance, which we relate to an upper-crustal earthquake, one of the strongest over the last 500 years, that affected the region on 13th February 2001 (Mw = 6.6, epicentre at 10 km depth, 30 km from the lake). The release of toxic bottom components such as hydrogen sulphide and high turbidity and turbulence of water caused major species turnover in the lake ecosystem, resulting in a massive fish kill and colonization by large cladocerans. Modern sediments still show slightly altered biota communities compared to pre-earthquake assemblages, indicating that the ecosystem has still not fully recovered

Working quality of new sugar-beet harvesters

W przeprowadzonych badaniach porównano dwa nowe samojezdne kombajny do zbioru buraka cukrowego typu Grimme Maxtron 620 i Kleine SF 20 ze sprawdzonymi w praktyce kombajnami Holmer Terra Dos T2 i Kleine SF 10-2. Badania wykonano we wrześniu 2005 r. w gospodarstwie rolnym Garzyn (Wielkopolska). Maszyny badano według metodyki Międzynarodowego Instytutu Buraka Cukrowego w Brukseli (I.I.R.B.). Dodatkowo ocenę uszkodzeń korzeni wykonano według Polskiej Normy. Uzyskane wyniki wskazują, że jakość pracy badanych maszyn była zbliżona w zakresie udziału zanieczyszczeń i jakości ogłowienia. Natomiast w zakresie strat plonu korzeni, wyniki są bardziej zróżnicowane, a najlepszy wynik uzyskał kombajn Grimme Maxtron.In the investigation two new self-propelled sugar-beet harvesters, Grimme Maxtron 620 and Kleine SF 20, were compared with the brands Holmer Terra Dos T2 and Kleine SF 10-2. The research was conducted in September 2005 in the Garzyn farm (Wielkopolska region). The harvesters were examined according to the methodology of the International Institute for Beet Research (IIRB) in Brussels. Additionally the estimation of roots breakages was made according to the Polish Norms System. Obtained results show that the work performance of the examined harvesters was similar in terms of impurities and topping quality. However as far as roots yield losses are concerned, the results are more variable, and the best result was obtained by the Grimme Maxtron equipment

The artificial neural nerwork as a helping tool in the process of non-linear data compression

Sieci autoasocjacyjne to sieci, które odtwarzają wartości wejściowe na swoich wyjściach. Działanie takie zdecydowanie ma sens, ponieważ rozważana sieć autoasocjacyjna posiada w warstwie środkowej (ukrytej) zdecydowanie mniejszą liczbą neuronów niż w warstwie wejściowej czy wyjściowej. Dzięki takiej budowie dane wejściowe muszą przecisnąć się przez swojego rodzaju zwężenie w warstwie ukrytej sieci, kierując się w do wyjścia. Dlatego też, w celu realizacji stawianego jej zadania reprodukcji informacji wejściowej na wyjściu, sieć musi się najpierw nauczyć reprezentacji obszernych danych wejściowych za pomocą mniejszej liczby sygnałów produkowanych przez neurony warstwy ukrytej, a potem musi opanować umiejętność rekonstrukcji pełnych danych wejściowych z tej "skompresowanej" informacji. Oznacza to, że sieć autoasocjacyjna w trakcie uczenia zdobywa umiejętność redukcji wymiaru wejściowych danych.An autoassociative network is one which reproduces its inputs as outputs. Autoassociative networks have at least one hidden layer with less units than the input and output layers (which obviously have the same number of layers as each other). Hence, autoassociative networks perform some sort of dimensionality reduction or compression on the cases. Dimensionality reduction can be used to pre-process the input data to encode Information in a smaller number of variables. This approach recognizes that the intrinsic dimensionality of the data may be lower than the number of variables. In other words, the data can be adequately described by a smaller number of variables, if the right transformation can be found

Mechanical weed control of sugar beet

W pracy przedstawiono ocenę eksploatacyjną pielnika nowej generacji podczas pielenia i nawożenia roztworem saletrzano mocznikowym buraków cukrowych w warunkach produkcyjnych. Badania były realizowane dla dwóch systemów sterowania pielnikiem podczas pracy: ręcznego i automatycznego. Sterowanie pielnikiem sposobem ręcznym odbywało się za pomocą dźwigni znajdującej się na pulpicie sterowniczym przez operatora siedzącego na siedzisku przymocowanym do ramy pielnika. Sterowanie automatyczne pielnikiem było wykonywane przez elektrohydrauliczny system sterowania opracowany przez firmę Agronomic. średnia wydajność efektywna pielnika Agronomic w okresie dwuletnich badań podczas pracy ze sterowaniem ręcznym wynosiła 1,6 haźh-1, a wydajność eksploatacyjna 0,86 haźh-1. Podczas pracy ze sterowaniem automatycznym średnia wydajność efektywna w latach prowadzenia bada wynosiła 3,5 haźh-1, a wydajność eksploatacyjna 1,86 haźh-1. Koszty pielęgnacji mechanicznej w burakach cukrowych dla jednego zabiegu agrotechnicznego przy sterowaniu ręcznym wynosiły około 131 złźha-1, a przy sterowaniu automatycznym około 67 złźha-1.This paper presents operating evaluation of a new generation hoe while hoeing of weeds and fertilizing of urea and ammonium nitrate solution in sugar beet production conditions. The research was carried out for the two control systems of hoes in operation: manual and automatic. Manual control of hoes, took place with a lever. The lever was on the control panel. Operator was sitting on the seat attached to the frame hoe. Automatic control of hoe was performed using electro-hydraulic control system developed by the Agronomic. Average effective field capacity of Agronomic hoe, during the two-year study, while working with manual control was 1.6 haźh-1 and using capacity was 0.86 haźh-1. While working with automatic control, average effective field capacity during the study was 3.5 haźh-1 and using capacity was 1.86 haźh-1. The cost of mechanical cultivation in sugar beet for one agricultural chemistry operation, for using manual control were about 131 złźha-1, and for automatic control were about 67 złźha-1

Evaluation of selected feeds differing in dietary lipids levels in feeding juveniles of wels catfish, Silurus glanis L

Background. Development of modern aquaculture and the increasing consumer demand provoke improvements in the complex breeding technologies of economically valuable fish species. Wels catfish, Silurus glanis L. (known also as the European catfish), because of its breeding and consumption values, becomes an increasingly common object of breeding. The objective of the presented work was the evaluation of selected feeds differing in dietary lipids levels applied in rearing the wels catfish fry under controlled conditions. Materials and methods. The feeding trial (60 days) was carried out with the wels catfish fry, weighing on average 55 g. The experiment was conducted under controlled conditions in an aquarium hall in 60-L flow-through tanks. During the growth test, the fish were given four commercial feeds of the same protein amount (45%) and graded fat levels (15%, 20%, 25%, and 30%). In the final evaluation of the feeding tests, the following rearing effectiveness indices were used: food conversion ratio (FCR), specific growth rate (SGR), protein efficiency ratio (PER), protein retention (PR), lipid retention (LR), and survival rate (SR). Conclusions were drawn on the basis of statistical analysis using Statistica computer software. Results. The wels catfish fed 20%-fat-content feed attained the highest individual weights. The other treatments yielded statistically significantly lower (P < 0.05) body weights. No statistically significant differences were found between the mean values of the specific growth rate (SGR). The values of feed conversion ratio (FCR) and protein efficiency ratio (PER) were approximately equal in the individual groups. The protein retention attained values from 28.2% to 33.0%, while fat retention ranged from 11.8% to 24.2%. No mortalities were recorded. The amount of fat in all groups increased significantly after the termination of the growth. The increase of fat amount in the feed was not correlated with the growth of fat amount in the fish body. The levels of the other body components increased, but no differences between the groups were found. Conclusion. Differentiated amounts of dietary lipids in the diet did not exert any effect on the rate of fish growth or on the proper utilization of the nutritive components in feeds