Application of a new reverse Monte Carlo algorithm to polyatomic molecular systems. I. Liquid water

Using a new reverse Monte Carlo algorithm, we present simulations that reproduce very well several structural and thermodynamic properties of liquid water. Both Monte Carlo, molecular dynamics simulations and experimental radial distribution functions used as input are accurately reproduced using a small number of molecules and no external constraints. Ad hoc energy and hydrogen bond analysis show the physical consistency and limitations of the generated RMC configurations. (C) 2001 American Institute of Physics.

MONTE-CARLO SIMULATION OF POLYAMPHOLYTE CHAINS

Polyampholyte copolymers containing both positive and negative monomers regularly dispersed along the chain were studied. The Monte Carlo method was used to simulate chains with charged monomers interacting by screened Coulomb potential. The neutral polyampholyte chains collapse due to the attractive electrostatic interactions. The nonneutral chains are in extended conformations due to the repulsive polyelectrolyte effects that dominate the attractive polyampholyte interactions. The results are in good agreement with experiment.

C - H ⋯ 0 and N - H ⋯ 0 hydrogen bonds in liquid amides investigated by monte carlo simulation

Monte Carlo simulations of liquid formamide, N-methylformamide (MF), and N, N-dimethytformamide (DMF) have been performed in the isothermal and isobaric ensemble at 298 K and 1 atm, aiming to investigate the C-H ⋯ O and N-H ⋯ O hydrogen bonds. The interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term on a rigid six-site molecular model with the potential parameters being optimized in this work. Theoretical values obtained for heat of vaporization and liquid densities are in good agreement with the experimental data. The radial distribution function [RDF, g(r)] obtained compare well with R-X diffraction data available. The RDF and molecular mechanics (MM2) minimization show that the C-H ⋯ O interaction has a significant role in the structure of the three liquids. These results are supported by ab initio calculations. This interaction is particularly important in the structure of MF. The intensity of the N - H ⋯ O hydrogen bond is greater in the MF than formamide. This could explain some anomalous properties verified in MF. © 1997 John Wiley & Sons, Inc.

Henneguya piaractus n.sp. (Myxozoa: Myxobolidae), a gill parasite of Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: characidae), in Brazil

Henneguya piaractus n.sp. was found from the gill filaments of Piaractus mesopotamicus (Characidae). Fishes were collected during a year from the reservoir at Centro de Aquicultura da UNESP, Jaboticabal, SP, Brazil. The prevalence of this parasite was 97.3% in the gills of farmed fish. Observations on spore development into the cysts were done. Studies with scanning electon microscopy were performed to observe the spore and cyst structure.

Coil to extended coil transition in polygalacturonic acid: Conductometric titration and monte carlo simulations

The conformational transition from coil to extended coil for polygalacturonic acid has been studied by conductometric titrations and Monte Carlo simulations. The results of conductometric titrations at different polymer concentrations have been analyzed using the model proposed by Manning,1 which describes the conductivity of polyelectrolitic solutions. This experimental approach provides the transport factor and the average distance between charged groups at different degrees of ionization (α). The mean distances between charged groups have been compared with the values obtained by Monte Carlo simulations. In these simulations the polymer chain is modeled as a self-avoiding random walk in a cubic lattice. The monomers interact through the unscreened Coulombic potential. The ratio between the end-to-end distance and the number of ionized beads provides the average distance between charged monomers. The experimental and theoretical values are in good agreement for the whole range of ionization degrees accessed by conductometric titrations. These results suggest that the electrostatic interactions seem to be the major contribution for the coil to extended coil conformational change. The small deviations for α ≤ 0.5 suggests that the stiffness of the chain, associated with local interactions, becomes increasingly significant as the fraction of charged groups is decreased. © 2000 American Chemical Society.

Composição corporal e índices biométricos do pacu, Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes, Characidae) submetido a ciclos alternados de restrição alimentar e realimentação

The present paper evaluated, through hepatosomatic/mesenteric fat indexes and body composition, the pacu energy utilization when submitted to alternated food restriction/refeeding cycles during the growout period. Juveniles were distributed in three pounds and submitted to different feeding programs: A (ad libitum daily feeding), B (4-week feeding restriction and 9-week refeeding) and C (6-week feeding restrictions and 7-week refeeding), totaling 13 weeks for each cycle (4 experimental cycles). At the end of the periods, fish were sampled to obtain biometrics and biochemical data. The results showed that, during the first two cycles, C treatment obtained the best compensatory growth. Carcass lipid and water contents were inversely related, with body fat decrease. Fishes under B and C treatment during food restriction utilized liver and mesentery energy stores. These parameters were re-established in the refeeding phase, in all cycles.

Alterações hematológicas e histopatológicas em pacu, Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes, Characidae), tratado com sulfato de cobre (CuSo4)

This paper evaluated the haematological and glycaemic parameters in Piaractus mesopotamicus (Osteichthyes, Characidae) infected with Monogenea Anacanthorus penilabiatus Boeger, Husak & Martins, 1995 (Dactylogyridae) after treatment with 0.50 mg/L and 1.00 mg/L of copper sulphate (CuSO4). The efficacy of the CuSO4 was observed in the first day after administration but not after eight, fifteen or thirty days. The histopathological analyses showed hyperplasia of the epithelium and circulatory changes in the gills. In the first day after treatment significant changes (P<0.05) in the total count of erythrocyte, leucocyte, mean corpuscular haemoglobin concentration (MCHC) were observed. The fishes treated with 0.50 mg/L showed decrease in the haemoglobin levels and in the percentage of neutrophils (P<0.05). The dose of 1.00 mg/L provoked increase of glycaemia but reduction in the lymphocytes percentage when compared with 0.50 mg/L in the 8th day. Fifteen days after 1.00 mg/L treatment, values of mean corpuscular volume (MCV) and special granulocitic cells (S.G.C.) percentage decreased. Nevertheless, increase of total leucocyte number was observed. Thirty days after treatment with 0.50 mg/L showed increased S.G.C. and treatment with 1.00 mg/L showed increased lymphocyte.

Características hematológicas, bioquímicas e biométricas de Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: Characidae) oriundos de cultivo intensivo

Hematological characteristics are important tools for diagnosis and prognostic features in fish population and they contribute to the comprehension of comparative physiology, phylogenetic relation, food habit and other ecological parameters. Red blood cell count (RBC), white blood cell count (WBC), thrombocytes counts, glucose, cortisol, hepatosomatic and splenosomatic relation were evaluated in Piaractus mesopotamicus. The values of hepatosomatic relation varied from 0.67% to 2.79% and splenosomatic relation from 0.011% to 0.108%. RBC 1.870 to 4.590 × 106/μL, hemoglobin concentration 5.7 to 12.1g/dL, haematocrit 24.0% to 40.0%, mean corpuscular volume 98.0 to 174.0 fL, mean corpuscular haemoglobin concentration 19.1 to 34.2g/dL, glucose 40.6 to 89.2mg/dL and cortisol 4.73 to 110.5ng/dL The number of total thrombocytes was 12,160.0 to 89,280.0/μL and WBC 2,019.0 to 47,473.0/μL. Differential count of leucocytes showed 54.1% limphocytes, 10.9% neutrophils, 10.3% monocytes, 9.9% PAS-positive granular leukocytes (PAS-GL), 6.7% eosinophils, 0.3% basophils and 7.8% immature leucocytes. Variation of these haematological characteristics in the same fish species was observed, being considered as the normal variation in the fish concerned. Hence it is incorrect to assume that biological characteristics in fishes are distributed normally.

Métodos de coleta de fezes e determinação dos coeficientes de digestibilidade da fração protéica e da energia de alimentos para o pacu, Piaractus mesopotamicus (Holmberg, 1887)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Co-feeding of pacu, Piaractus mesopotamicus Holmberg (1887), larvae with Artemia naupili and a microencapsulated diet

Aiming at a precocious substitution of live prey by artificial diet, a 20-day experiment with pacu, Piaractus mesopotamicus, larvae using co-feeding and abrupt weaning strategies was set up. At the end of the experiment, larvae fed Artemia showed the best results (P < 0.05) in weight, total length and biomass, compared with other treatments. Larvae fed exclusively a microencapsulated diet never ingested the diet. Diet ingestion in co-fed and abrupt-weaned larvae was low, but did increase during the experiment; however, Artemia influenced diet ingestion on co-fed larvae. Careful considerations should be given to diet processing and formulation to ensure survival and growth of larvae fed exclusively on prepared diets. © 2005 by The Haworth Press, Inc. All rights reserved.

Efeitos do parasitismo sobre a estrutura branquial de Leporinus macrocephalus Garavello e Britsk, 1988 (Anastomidae) e Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes:Characidae).

This work described the lesions caused in different species of fish by gill parasites from fee-fishing at Guariba, State of São Paulo. The research was developed from april, 1997 to march to 1999, seeking to verified the kind tissues lesions from fish. Of these, forty and seven were Leporinus macrocephalus and fifty and five Piaractus mesopotamicus. About 87.2% of the L. macrocephalus, and 58.1% of the P. mesopotamicus were sponged by several species of parasites. The parasite most abundant in L. macrocephalus was Piscinoodinium pillulare, while monogenean, Trichodina sp and myxosporidian infected P. mesopotamicus. Severe gill lesions have been observed in L. macrocephalus and P. mesopotamicus caused by monogenean, P. pillulare e Trichodina sp. parasitism, such as intersticial hemorrhage, sub-epithelium edema, inflammation, epitelial hiperplasy in filaments and lamina, proliferation of mucosal cells and laminar fusion.

Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae): Acid phosphatase and ATPase activities localization in salivary glands of females during the feeding period

This study investigates the presence and the localization of acid phosphatase and ATPase in the salivary glands of Rhipicephalus (Boophilus) microplus female ticks during feeding. Semi-engorged females showed a larger amount of acid phosphatase compared to those at beginning of feeding, localized mainly in the apical portion of the secretory cells, and in the basal labyrinth of the interstitial cells. Ultrastructural observations also demonstrated its presence in secretion granules and inside some nuclei of secretory cells at beginning of feeding. Acid phosphatase in a free form probably has a hemolymph and/or ribosomal origin and participates in salivary gland secretion control. ATPase was detected in basal membrane of all types of acini and/or in the cytoplasm of the secretory cells at both feeding stages. The enzyme activities found strongly suggests that cell death by apoptosis occurs during the degenerative process. © 2006 Elsevier Inc. All rights reserved.

Chronological Monte Carlo-based assessment of distribution system reliability

Regulatory authorities in many countries, in order to maintain an acceptable balance between appropriate customer service qualities and costs, are introducing a performance-based regulation. These regulations impose penalties, and in some cases rewards, which introduce a component of financial risk to an electric power utility due to the uncertainty associated with preserving a specific level of system reliability. In Brazil, for instance, one of the reliability indices receiving special attention by the utilities is the Maximum Continuous Interruption Duration per customer (MCID). This paper describes a chronological Monte Carlo simulation approach to evaluate probability distributions of reliability indices, including the MCID, and the corresponding penalties. In order to get the desired efficiency, modern computational techniques are used for modeling (UML -Unified Modeling Language) as well as for programming (Object- Oriented Programming). Case studies on a simple distribution network and on real Brazilian distribution systems are presented and discussed. © Copyright KTH 2006.

Avaliação comparativa da eficácia de fitoterápicos e produtos químicos carrapaticidas no controle do boophilus microplus (Canestrini, 1887) por meio do biocarrapaticidograma

The aim of this research was to evaluate the efficacy of plant extracts and chemical products for the control of Boophilus microplus. Three commercial products for the control of Boophilus microplus were in vitro evaluated, chemical compounds of cypermethrin + DDVP and organophosphate as recomended by the manufacturer, and also four plant extracts, Azadirachta indica (1%), Cymbopogon densiflorus, Lippia alba and Ipomoea asarifolia at different concentrations. The results showed that the chemical compounds tested had efficacy lower than 95% against the Boophilus microplus samples in the experiment. The extracts of all plants have shown some biological activity in the mortality of ingurgitated females and inhibition of egg crash, however the extract of Azadirachta indica presented efficacy higher than 95% in all tested concentrations, being the best sample tested in this experiment.