Effectiveness of neem seed oil (Azadirachta indica A. Juss: Meliaceae) on Syllepte derogata Fabricius, Lepidoptera: Pyralidae

Objective: Synthetic insecticides have long been used for cotton protection,  resulting in pest resistance, toxicity and environmental pollution. Biopesticides have been suggested as alternatives to synthetic pesticides. Both field and laboratory experiments were conducted to evaluate the effectiveness of neem oil in controlling Syllepte derogata (Fabricius), a cotton phyllophagous pest.Methodology and Results: In the field trials, effect of neem oil was compared to that of conventional insecticides; while in the laboratory direct larval immersion and leaf dip method using EMA SUPER 56DC and neem oil were tested. Decrease in damage by S. derogata for about 63 and 86% was recorded with neem oil and synthetic insecticides. In the laboratory, the mortality of S. derogata after 24 hours exposure to neem oil and Ema Super was significantly higher (2.5 to 100%) than that of the control. The mortality of larvae of S. derogata was positively correlated with the concentration of neem oil and exposure time. Lethal Concentration (LC50) after 24 hours exposure of larvae was respectively 4.03 104 ml/l and 51.13 ml/l forleaf dipping method and larval immersion.Conclusion and application of results: Overall, these results showed the efficacy of neem oil in controlling S. derogata, as a biopesticide. This oil could also  constitute a successful alternative to synthetic pesticides. However, the  effectiveness of neem oil appeared to be weakened by the rapid degradation of the active substances, azadirachtin in particular. Indeed, azadirachtin, the main active ingredient of neem is photo and heat labile. It easily degrades under high solar radiations and high temperatures, hence the need for stabilization.Keywords: Phyllophagous pest, integrated pest management, leaf-dipping method, larval immersion, Lethal Concentration

30 years of collaboration

We highlight some of the most important cornerstones of the long standing and very fruitful collaboration of the Austrian Diophantine Number Theory research group and the Number Theory and Cryptography School of Debrecen. However, we do not plan to be complete in any sense but give some interesting data and selected results that we find particularly nice. At the end we focus on two topics in more details, namely a problem that origins from a conjecture of Rényi and Erdős (on the number of terms of the square of a polynomial) and another one that origins from a question of Zelinsky (on the unit sum number problem). This paper evolved from a plenary invited talk that the authors gaveat the Joint Austrian-Hungarian Mathematical Conference 2015, August 25-27, 2015 in Győr (Hungary)

Oxidation Kinetics of Mixtures of Iso-Octane with Ethanol or Butanol in a Jet-Stirred Reactor: Experimental and Modeling Study

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Numerical and experimental study of ethanol combustion and oxidation in laminar premixed flames and in jet-stirred reactor

The main objectives of this research consist in achieving both experimental and numerical studies of the combustion and oxidation of ethanol. Experimental mole fraction profiles of chemical species (stable, radical, and intermediates) were measured in three C2H5OH/O2/Ar flat premixed flames stabilized at low pressure (50mbar) and with equivalence ratios equal to 0.75, 1, and 1.25, respectively. The experimental setup used to determine the structure of one-dimensional laminar premixed flames consists of a molecular beam mass spectrometer system (MBMS) combined with electron impact ionization (EI). The oxidation of ethanol was also experimentally studied using a fused silica jet-stirred reactor (JSR). Experiments were performed in the temperature range 890-1250K, at 1atm, at four equivalence ratios equal to 0.25, 0.5, 1, and 2 and with an initial fuel concentration of 2000ppm. A kinetic study was conducted in order to simulate all experimental data measured. It enabled building a kinetic mechanism by thoroughly reviewing the available literature and by taking into account specificities of the two kinds of experiments performed. Validity of the mechanism was also checked against experimental results previously published (ethanol oxidation in a JSR at 10. atm, ignition in a shock tube, combustion in premixed, partially-premixed, and non-premixed flames). This mechanism ensures a reasonably good modelling of the combustion and oxidation of ethanol over the wide range of experimental conditions investigated. © 2010 The Combustion Institute

Oxidation kinetics of n-nonane: Measurements and modeling of ignition delay times and product concentrations

International audienceOxidation of n-nonane (n-C9H20) under conditions of high dilution (>97% inert) has been studied over a broad range of temperature (530 < T (K) < 1591) and equivalence ratio (0.5, 1.0, 2.0) at pressures near 1 and 10 atm using shock-tube and jet-stirred reactor facilities. Excited-state hydroxyl radical (OH*) time histories were measured using emission spectroscopy of OH behind reflected shock waves from which ignition delay and peak formation times were extracted. Temperature-dependent species concentrations were measured using gas chromatography, FTIR, TCD, and FID of jet-stirred reactor combustion products. Ignition delay times show a strong dependence on equivalence ratio, increasing by a factor of nearly 5 at both 1 and 10.4 atm. An overall ignition delay time correlation was constructed, revealing a pressure dependence of P^^0.48. Experimental data from both facilities were utilized to develop and validate a chemical kinetics mechanism for n-nonane oxidation. Kinetic model predictions of ignitiondelay time compare well, particularly for the lean and stoichiometric mixtures. Jet-stirred reactor data show excellent overall agreement with major species, as well as alkanes and alkenes present in the combustion products. Alkenes up to C9 were produced from n-nonane oxidation and ethylene, a dominant product of n-nonane thermal decomposition, is identified as the most abundant among them. The present studyprovides an extensive series of fundamental measurements on n-nonane oxidation, resulting in the formulation of a mechanism used to describe and predict associated reaction kinetics

A jet-stirred reactor and kinetic modeling study of ethyl propanoate oxidation

International audienceA jet-stirred reactor study of ethyl propanoate, a model biodiesel molecule, has been carried out at 10 atm pressure, using 0.1% fuel at equivalence ratios of 0.3, 0.6, 1.0 and 2.0 and at temperatures in the range 750–1100 K with a constant residence time of 0.7 seconds. Concentration profiles ofethyl propanoate were measured together with those of major intermediates, ethylene, propanoic acid, methane and formaldehyde, and major products, water, carbon dioxide and carbon monoxide. This data was used to further validate a previously published detailed chemical kinetic mechanism, containing 139 species and 790 reversible reactions. It was found that this mechanism required a significant increase in the rate constant of the six-centered unimolecular elimination reaction which produces ethylene and propanoic acid in order to correctly reproduce the measured concentrations of propanoic acid. The revised mechanism was then used to re-simulate shock tube ignition delay data with good agreement observed. Rate of production and sensitivity analyses were carried out under the experimental conditions, highlighting the importance that ethylene chemistry has on the overall reactivity of the system

Experimental and kinetic modeling of methyl octanoate oxidation in an opposed-flow diffusion flame and a jet-stirred reactor

International audienceNew experimental results, consisting of concentration profiles of stable species as a function of temperature, were obtained for the oxidation of methyl octanoate in a jet stirred reactor (JSR) at 0.101 MPa, 0.5 < phi < 2 and 800 < T (K) < 1350. In addition, new experimental data, consisting of concentration profiles of stable species as a function of distance from fuel port, generated in an opposed-flow diffusion flame at 0.101 MPa are presented. A detailed chemical kinetic model was developed to study the oxidation of methyl octanoate (CAS 111-11-5), a model compound for biodiesel fuels, under the present conditions. The kinetic model consists of 383 chemical species and 2781 chemical reactions (most of them reversible). Experimentally, the oxidation of methyl octanoate in the JSR at atmospheric pressure does not show low temperature and negative temperature coefficient behavior, whereas hot ignition occurs at about 800 K. The present modeling results are in reasonably good agreement with the experimental data, describing the intermediate species measured in the jet stirred reactor and in opposed-flow diffusion flame experiments

Biologically derived diesel fuel and NO formation

International audiencePart 1 of this two part series presented a chemical kinetic model for the simulation of high pressure shock tube pyrolysis and oxidation data of two representative biodiesel surrogate components and the application of this model for predicting prompt NO at practical diesel combustion conditions. The present work discusses in greater detail the model’s development, structure, and rate parameters as well as expands the model’s validation range to include complementary 10 atm jet stirred reactor (JSR) oxidation experiments conducted at lower temperatures (550–1200 K) and longer reaction times of 0.7 s. In addition, shock tube ignition delay measurements of 1-heptene and 1,6-heptadiene, analogs of the hydrocarbon side chains of the methyl esters, have also been performed and are presented to further constrain the model

Experimental and Numerical Study of F-T/Biodiesel/Bioethanol Surrogate Fuel Oxidation in Jet-Stirred Reactor

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