Low-traffic limit and first-passage times for a simple model of the continuous double auction

We consider a simplified model of the continuous double auction where prices are integers varying from 1 to N with limit orders and market orders, but quantity per order limited to a single share. For this model, the order process is equivalent to two M∕M∕1 queues. We study the behaviour of the auction in the low-traffic limit where limit orders are immediately matched by market orders. In this limit, the distribution of prices can be computed exactly and gives a reasonable approximation of the price distribution when the ratio between the rate of order arrivals and the rate of order executions is below 1∕2. This is further confirmed by the analysis of the first-passage time in 1 or N

Osetljivost kukuruza, suncokreta i ječma na rezidualno delovanje klomazona u zemljištu

Sensitivity of maize, sunflower and barley to clomazone residues in loamy soil was assessed in the study using bioassay. Clomazone was applied at a series of concentrations from 0.12 to 12 mg a.i./kg of soil. After 14 days, morphological (shoot height, fresh and dry weight) and physiological (content of carotenoids, chlorophyll a and chlorophyll b) parameters were measured. The results showed that morphological parameters are not valid indicators of clomazone sensitivity. Based on the results showing inhibition of the physiological parameters, I50 values were calculated and used to estimate the difference in sensitivity between the species tested. Sunflower was the most sensitive species, while the difference in sensitivity between maize and barley was not significant. Nomenclature: clomazone (2-(2-chlorbenzyl)-4,4-dimethyl-1,2-oxazolidin-3-one), maize (Zea mays L.), sunflower (Helianthus annuus L.), barley (Hordeum vulgare L.).U radu je ispitivana osetljivost kukuruza, suncokreta i ječma na rezidualno delovanje klomazona u zemljištu tipa ilovače, metodom biotesta. Klomazon je primenjen u seriji koncentracija 0,12-12 mg a.s./kg zemljišta. Nakon 14 dana rasta biljaka mereni su morfološki (visina, sveža i suva masa izdanka) i fiziološki parametri (sadržaj karotenoida, hlorofila a i hlorofila b). Konstatovano je da morfološki parametri nisu pouzdano merilo osetljivosti na klomazon. Prema ostvarenim procentima inhibicije za merene fiziološke parametre izračunate su vrednosti I50, a na osnovu njih utvrđene su razlike u osetljivosti ispitivanih biljnih vrsta. Najosetljiviji je bio suncokret, dok se kukuruz i ječam nisu međusobno značajno razlikovali

Ergodic transition in a simple model of the continuous double auction

We study a phenomenological model for the continuous double auction, whose aggregate order process is equivalent to two independent M/M/1 queues. The continuous double auction defines a continuous-time random walk for trade prices. The conditions for ergodicity of the auction are derived and, as a consequence, three possible regimes in the behavior of prices and logarithmic returns are observed. In the ergodic regime, prices are unstable and one can observe a heteroskedastic behavior in the logarithmic returns. On the contrary, non-ergodicity triggers stability of prices, even if two different regimes can be seen

Interplay of simple stochastic games as models for the economy

summary:Using the interplay among three simple exchange games, one may give a satisfactory representation of a conservative economic system where total wealth and number of agents do not change in time. With these games it is possible to investigate the emergence of statistical equilibrium in a simple pure-exchange environment. The exchange dynamics is composed of three mechanisms: a decentralized interaction, which mimics the pair-wise exchange of wealth between two economic agents, a failure mechanism, which takes into account occasional failures of agents and includes wealth redistribution favoring righer agents, and a centralized mechanism, which describes the result of a redistributive effort. According to the interplay between these three mechanisms, their relative strength, as well as the details of redistribution, different outcomes are possible

Mean values and error bars.

<p>Mean values and error bars of the standard deviation (a), kurtosis (b) of log-returns and the first-lag autocorrelation of absolute log-returns (c) as functions of the parameter , estimated from 1000 Monte Carlo simulations.</p

Sample autocorrelation functions for the absolute log-returns.

<p>(a) ergodic case (); (b) non-ergodic case for () and (c) non-ergodic case for ().</p

Multiresidue Analysis of Pesticides in Soil by Liquid-Solid Extraction Procedure

A multiresidue method for simultaneous determination of four pesticides (diazinon,acetochlor, aldrine and carbofuran) belonging to different pesticide groups, extractedfrom soil samples, is described. The method presented is based on liquid-solid extraction(LSE) and determination of pesticides, i.e. the pesticides were extracted by methanol-acetone mixture, purified on florisil column and eluted by ethyl acetate-acetone mixture.Optimization of the main parameters affecting the LSE procedure, such as the choiceof purification sorbent, as well as the elution solvent and its volume, were investigated indetails and optimized. Also, validation of the proposed method was done.Gas chromatography-mass spectrometry (GC-MS) was used for detection and quantificationof the pesticides studied. Relative standard deviation (RSD) and recovery values formultiple analysis of soil samples fortified with 30 μg/kg of each pesticide were below 8%and higher than 89%, respectively. Limits of detection (LOD) for all the compounds studiedwere less than 4 μg/kg

Tetraoxanes as inhibitors of apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii growth and anti-cancer molecules

New cyclohexylidene 1,2,4,5-tetraoxanes with polar guanidine and urea based groups were synthesized and evaluated for their antimalarial activity against chloroquine resistant and susceptible Plasmodium falciparum strains. The derivatives showed moderate, nM range antimalarial activities and low cytotoxicity. The N-phenylurea derivative 24 exhibited the best resistance indices (RIW2 = 0.44, RITM91C235 = 0.80) and was not toxic against human normal peripheral blood mononuclear cells (IC50 gt 200 mu M). Seven derivatives were tested in vitro against four human cancer cell lines and they demonstrated high selectivity toward leukaemia K562 cells. One compound, derivative 21 with a primary amino group, was the first tetraoxane tested in vivo against Toxoplasma gondii as another apicomplexan parasite. Subcutaneous administration at a dose of 10 mg kg(-1) day(-1) for 8 days allowed the survival of 20 % of infected mice, thus demonstrating the high potential of tetraoxanes for the treatment of apicomplexan parasites

Cucumber susceptibility to simulated soil residues of clomazone

A laboratory bioassay was conducted to investigate the susceptibility of cucumber to the residual activity of clomazone in loamy and sandy soils. The effects of three different levels of soil moisture (20, 50 and 70% field capacity - FC) was also examined. Clomazone was applied in concentration series of 0.047-6 mg a.i./kg soil. Plants grew for 21 days, upon which period physiological parameters (content of carotenoids, chlorophyll ɑ and chlorophyll b) were measured. Clomazone caused leaf bleaching and reduction in pigments content in cucumber leaves in both types of soil at all levels of soil moisture, and the degree of change depended on application rates. Inhibition was higher in plants grown in the sandy soil, while the least sensitive were cucumber plants grown in both types of soil with 20% FC. The findings in this study showed moderate cucumber susceptibility to clomazone residues in loamy and sandy soils