Spectrophotometric detection of arsenic using flow-injection hydride generation following sorbent extraction preconcentration

An automated system with a C-18 bonded silica gel packed minicolumn is proposed for spectrophotometric detection of arsenic using flow-injection hydride generation following sorbent extraction preconcentration. Complexes formed between arsenic(III) and ammonium diethyl dithiophosphate (ADDP) are retained on a C-18 sorbent. The eluted As-DDP complexes are merged with a 1.5% (w/v) NaBH4 and the resulting solution is thereafter injected into the hydride generator/gas-liquid separator. The arsine generated is carried out by a stream of N-2 and trapped in an alkaline iodine solution in which the analyte is determined by the arsenomolybdenum blue method. With preconcentration time of 120 s, calibration in the 5.00-50.0 mu g As l(-1) range and sampling rate of about 20 samples h(-1) are achieved, corresponding to 36 mg ADDP plus 36 mg ammonium heptamolybdate plus 7 mg hydrazine sulfate plus 0.7 mg stannous chloride and about 7 mi sample consumed per determination. The detection limit is 0.06 mu g l(-1) and the relative standard deviation (n = 12) for a typical 17.0 mu g As l(-1) sample is ca. 6%. The accuracy was checked for arsenic determination in plant materials from the NIST (1572 citrus leaves; 1573 tomato leaves) and the results were in agreement with the certified values at 95% confidence level. Good recoveries (94-104%) of spiked tap waters, sugars and synthetic mixtures of trivalent and pentavalent arsenic were also found. (C) 1999 Elsevier B.V. B.V. All rights reserved.

On-line preconcentration and speciation analysis of Cr(III) and Cr(VI) using baker's yeast cells immobilised on controlled pore glass

A study was undertaken to evaluate Saccharonzyces cerevisiae as a substrate for the biosorption of Cr(III) and Cr(VI) aiming to the selective determination of these species in aqueous solutions. The yeast cells were covalently immobilised on controlled pore glass (CPG), packed in a minicolumn and incorporated in an on-line flow injection system. The effect of chemical and physical variables affecting the biosorption process was tested in order to select the optimal analytical conditions for the Cr retention by S. cerevisiae. Cr(III) was retained by the immobilised cells and Cr(VI) were retained by CPG. The speciation was possible by selective and sequential elution of Cr(III) with 0.05 mol L-1 HCl and 2.0 mol L-1 HNO3 for Cr(VI). The influence of some concomitant ions up to 20 mg L-1 was also tested. Quantitative determinations of Cr were carried out by means of inductively coupled plasma optical emission spectrometry (ICP OES). Preconcentration factors of 12 were achieved for Cr(III) and 5 for Cr(VI) when 1.7 mL of sample were processed reaching detection limits of 0.45 for Cr(III) and 1.5 mu g L-1 for Cr(VI). The speciation of inorganic Cr in different kinds of natural waters was performed following the proposed method. Spiked water samples were also analysed and the recoveries were in all cases between 81 and 103%. (c) 2005 Elsevier B.V. All rights reserved.

Agent-based model to rural-urban migration analysis

In this paper, we analyze the rural-urban migration phenomenon as it is usually observed in economies which are in the early stages of industrialization. The analysis is conducted by means of a statistical mechanics approach which builds a computational agent-based model. Agents are placed on a lattice and the connections among them are described via an Ising-like model. Simulations on this computational model show some emergent properties that are common in developing economies, such as a transitional dynamics characterized by continuous growth of urban population, followed by the equalization of expected wages between rural and urban sectors (Harris-Todaro equilibrium condition), urban concentration and increasing of per capita income. (c) 2005 Elsevier B.V. All rights reserved.

Population structure and genetic variability in the Murrah dairy breed of water buffalo in Brazil accessed via pedigree analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of the ethical aspects of professional confidentiality in dental practice

From the point of view of deontological ethics, privacy is a moral right that patients are entitled to and it is bound to professional confidentiality. Otherwise, the information given by patients to health professionals would not be reliable and a trustable relationship could not be established. The aim of the present study was to assess, by means of questionnaires with open and closed questions, the awareness and attitudes of 100 dentists working in the city of Andradina, São Paulo State, Brazil, with respect to professional confidentiality in dental practice. Most dentists (91.43%) reported to have instructed their assistants on professional confidentiality. However, 44.29% of the interviewees showed to act contradictorily as reported talking about the clinical cases of their patients to their friends or spouses. The great majority of professionals (98.57%) believed that it is important to have classes on Ethics and Bioethics during graduation and, when asked about their knowledge of the penalties imposed for breach of professional confidentiality, only 48.57% of them declared to be aware of it. Only 28.57% of the interviewees affirmed to have exclusive access to the files; 67.14% reported that that files were also accessed by their secretary; 1.43% answered that their spouses also had access, and 2.86% did not answer. From the results of the present survey, it could be observed that, although dentists affirmed to be aware of professional confidentiality, their attitudes did not adhere to ethical and legal requirements. This stand of health professionals has contributed to violate professional ethics and the law itself, bringing problems both to the professional and to the patient.

New approach to four-phase transmission systems: analysis of the transient response and the possible voltage surges

This study describes a technical analysis of a four-phase line as a transmission system alternative. An analysis in the frequency and the time domains is performed to evaluate the electrical characteristics and the transient response of a generic four-phase system compared with those of a conventional three-phase transmission system. The technical features of this non-conventional system are discussed and reviewed based on the current literature. Thus, a new analysis of the four-phase system is presented that emphasises several technical characteristics that have not been discussed in previous studies.

STOMACH CONTENTS ANALYSIS of WHITE MARLIN (TETRAPTURUS ALBIDUS) CAUGHT OFF SOUTHERN and SOUTHEASTERN BRAZIL: A BAYESIAN ANALYSIS.

This study proposes to ascertain the importance of each alimentary category in the Tetrapturus albidus diet composition, as well as to propose the use of the Bayesian approach for analysis of these data. The stomachs were collected during fishing cruises carried out by the Santos-SP longliner from July 2007 to June 2008. For Bayesian model formulation, each alimentary item was clustered in four food categories as: teleost, cephalopod, crustaceans, and others. To estimate the proportion of each food category, the multinomial model with Dirichlet conjugate prior distribution was used. After the stomach contents analysis, 133 food items were identified, which belonged to 9 taxa. The most important food category is constituted by cephalopod molluscs, followed by teleost fishes. The food category comprised of crustaceans presents a low contribution and in this case it could be considered to be an accidental food item. The Bayesian approach means a distinct view in relation to traditional methods, as it permits one to incorporate information obtained from the literature. It should be useful to analyse great top predators, which are usually caught in small numbers.

Sewage sludge coke estimation using thermal analysis

The imposition of more stringent legislation by CETESB in the State of So Paulo (Brazil) governing the disposal and utilization of sewage sludge, coupled with the growth in its generation has prompted a drive for alternative uses of sewage sludge. One option that is especially promising, due to its potential to valorize sludge, is its conversion into carbonaceous adsorbents or coke for industrial effluents treatment. Thus, a methodology is presented to estimate the coke produced from the sludge of a sewage treatment station using thermal analysis. The used sewage sludge, which comes from aerobic treatment, was collected in the wastewater treatment station of Barueri, one of the largest of the So Paulo metropolitan area. The sludge samples were collected, dried, ground, and milled until they passed an ABNT 200 sieve. The inert ambient used during its thermal treatment produces inorganic matter and coke as residual materials. Coke formation occurs in the 200-500 A degrees C range and, between 500 and 900 A degrees C, its thermal decomposition occurs. The highest formation of coke occurs at 500 A degrees C.

Defining the student burnout construct: a structural analysis from three burnout inventories

College student burnout has been assessed mainly with the Maslach Burnout Inventory (MBI). However, the construct's definition and measurement with MBI has drawn several criticisms and new inventories have been suggested for the evaluation of the syndrome. A redefinition of the construct of student burnout is proposed by means of a structural equation model, reflecting burnout as a second order factor defined by factors from the MBI-Student Survey (MBI-SS); the Copenhagen Burnout Inventory-Student Survey (CBI-SS) and the Oldenburg Burnout Inventory-Student Survey (OLBI-SS). Standardized regression weights from Burnout to Exhaustion and Cynicism from the MBI-SS scale, Personal Burnout and Studies Related Burnout from the CBI, and Exhaustion and Disengagement from OLBI, show that these factors are strong manifestations of students' burnout. For college students, the burnout construct is best defined by two dimensions described as "physical and psychological exhaustion" and "cynicism and disengagement."

Labeling index in pituitary adenomas evaluated by means of MIB-1: is there a prognostic role? A critical review

Objective: The present article presents an overview of the literature, and analyses the methods and the primary questions related to assessment of proliferation index using the Ki-67/MIB-1 labeling index in pituitary adenomas. Although atypical adenomas are characterized by their atypical morphological features by an elevated mitotic index, a Ki-67 (MIB-1) labeling index greater than 3% and extensive nuclear staining for p53, use of the proliferation index (LI) of pituitary adenomas in assessing the degree of tumor aggressiveness is a controversial topic in the literature, and there are disparate results involving many studies.Methods: A review of literature was carried out to correlate the role of Ki-67 LI and its correlation with clinical findings, tumor size, invasiveness, recurrence, adenoma subtype, adenoma doubling time, and pituitary carcinomas is addressed. Results: The prognosis cannot be predicted on the basis of the Ki-67 LI alone. Although there is no direct relation between Ki-67 LI and some of these variables and controversial data were found regarding some topics, our review justify the use of Ki-67 in the analysis of pituitary adenomas as an additional information for clinical decision.Conclusion: Although assessment of proliferative may be helpful in predicting subsequent tumor recurrence or invasiveness, there are many other important and as yet unidentified factors pituitary tumors. It is clear that further research is needed to clarify these molecular mechanisms to predict those with a potentially poor clinical outcome.

Faunal analysis of the species Anastrepha in the fruit growing complex Gaviao River, Bahia, Brazil

Besides being considered the greatest pests of fruit growing, fruit flies constitute a large obstacle to the growth of the exportation of fresh fruit. Knowledge of the structure of fruit fly communities is of great importance to the bioecological studies of these insects, but there is a lack of information about the faunistic composition of fruit flies in Brazil. The objective of this work was to analysis the composition of the species of Anastrepha, in eleven mango orchards of the fruit growing complex Gaviao River, Bahia, Brazil. These studies were done in 2004 and 2005, in Anage, Caraibas and Belo Campo town, 23 McPhail traps, which collected 798 female fruit flies from the genus Anastrepha. The structure of these communities was evaluated in each orchard by means of faunistic indexes frequency, constancy, dominance, diversity and similarity. The number of species varied from four to eight in each orchard; and the following species was recorded: Anastrepha fraterculus (Wiedemann), Anastrepha obliqua (Macquart), Anastrepha dissimilis Stone, Anastrepha amita Zucchi, Anastrepha distincta Greene, Anastrepha pickeli Lima. Anastrepha sororcula Zucchi and Anastrepha zenildae Zucchi. The most frequent and dominant species were A. fraterculus and A. obliqua. The indexes of diversity varied from 1.01 to 1.62. In general, the similarity between orchards was high (above 55.0%). We observed the formation of groups, one constituted by Frutvale, Carlan, Santa Clara and Panorama orchards; another composed of Cofet, Campo Gaviao and Ouro Verde and a third group formed by Boa Vista orchard. Barra da Onca and Arruda are distinguished from other orchards.

Uma metodologia para o controle de seguranca dinamica de sistemas de energia eletrica

This work presents an algorithm for the security control of electric power systems using control actions like generation reallocation, determined by sensitivity analysis (linearized model) and optimization by neural networks. The model is developed taking into account the dynamic network aspects. The preventive control methodology is developed by means of sensitivity analysis of the security margin related with the mechanical power of the system synchronous machines. The reallocation power in each machine is determined using neural networks. The neural network used in this work is of Hopfield type. These networks are dedicated electric circuits which simulate the constraint set and the objective function of an optimization problem. The advantage of using these networks is the higher speed in getting the solutions when compared to conventional optimization algorithms due to the great convergence rate of the process and the facility of the method parallelization. Then, the objectives are: formulate and investigate these networks implementations in determining. The generation reallocation in digital computers. Aiming to illustrate the proposed methodology an application considering a multi-machine system is presented.

A theoretical and experimental analysis of cold-formed steel shapes subjected to bending - Channel and simple lipped channel

Cold-formed steel shapes have been widely employed in steel construction, where they frequently offer a lower cost solution than do traditional laminated shapes. A classic application of cold-formed steel shapes is purlins in the roof panel of industrial buildings, connected to the roof panel by means of screws. The combined effect of these two elements has been the subject of investigations in some countries. Design criteria were included in the AISI Code in 1991 and 1996. This paper presents and discusses the results obtained from bending tests carried out on shapes commonly used in Brazil, i.e., the channel and the simple lipped channel, Tests were carried out on double shapes with 4.5 and 6.0 meter spans, which were subjected to concentrated loads and braced against each other on the supports and at intermediary points in three different load situations. The panel shape was also analyzed experimentally, simulating the action of wind by means of a vacuum box designed specifically for this purpose. The test results were then compared to those obtained through the theoretical analysis, enabling us to extract important information upon which to base proposed design criteria for the new Brazilian code.

Behavior of bromide in the photoelectrocatalytic process and bromine generation using nanoporous titanium dioxide thin-film electrodes

In this study, the photoelectrocatalytic behavior of bromide and generation of bromine using TiO2 was investigated in the separate anode and cathode reaction chambers. Our results show that the generation of bromine begins around a flatband potential of -0.34 V vs. standard calomel electrode (SCE) at pH 3.0 under UV illumination and increases with an increase in positive potential, finally reaching a steady-state concentration at 1.0 V vs. SCE. Maximum bromine formation occurs over the range of pH 4-6, decreasing sharply at conditions where the pH > 7. © 2003 Elsevier Ltd. All rights reserved.

Network reconfiguration and loss allocation for distribution systems with distributed generation

Distribution systems with distributed generation require new analysis methods since networks are not longer passive. Two of the main problems in this new scenario are the network reconfiguration and the loss allocation. This work presents a distribution systems graphic simulator, developed with reconfiguration functions and a special focus on loss allocation, both considering the presence of distributed generation. This simulator uses a fast and robust power flow algorithm based on the current summation backward-forward technique. Reconfiguration problem is solved through a heuristic methodology and the losses allocation function, based on the Zbus method, is presented as an attached result for each obtained configuration. Results are presented and discussed, remarking the easiness of analysis through the graphic simulator as an excellent tool for planning and operation engineers, and very useful for training. © 2004 IEEE.