Extension of a Recent Method for Obtaining Exact Solutions of the Bruce and Klute Equation

A method based on a specific power-law relationship between the hydraulic head and the Boltzmann variable was recently presented. We generalized this relationship to a range of powers and extended the solution to include the saturated zone. As a result, the new solution satisfies the Bruce and Klute equation exactly.

A log-extended Weibull regression model

A bathtub-shaped failure rate function is very useful in survival analysis and reliability studies. The well-known lifetime distributions do not have this property. For the first time, we propose a location-scale regression model based on the logarithm of an extended Weibull distribution which has the ability to deal with bathtub-shaped failure rate functions. We use the method of maximum likelihood to estimate the model parameters and some inferential procedures are presented. We reanalyze a real data set under the new model and the log-modified Weibull regression model. We perform a model check based on martingale-type residuals and generated envelopes and the statistics AIC and BIC to select appropriate models. (C) 2009 Elsevier B.V. All rights reserved.

Log-modified Weibull regression models with censored data: Sensitivity and residual analysis

This paper proposes a regression model considering the modified Weibull distribution. This distribution can be used to model bathtub-shaped failure rate functions. Assuming censored data, we consider maximum likelihood and Jackknife estimators for the parameters of the model. We derive the appropriate matrices for assessing local influence on the parameter estimates under different perturbation schemes and we also present some ways to perform global influence. Besides, for different parameter settings, sample sizes and censoring percentages, various simulations are performed and the empirical distribution of the modified deviance residual is displayed and compared with the standard normal distribution. These studies suggest that the residual analysis usually performed in normal linear regression models can be straightforwardly extended for a martingale-type residual in log-modified Weibull regression models with censored data. Finally, we analyze a real data set under log-modified Weibull regression models. A diagnostic analysis and a model checking based on the modified deviance residual are performed to select appropriate models. (c) 2008 Elsevier B.V. All rights reserved.

General results for the beta-modified Weibull distribution

We study in detail the so-called beta-modified Weibull distribution, motivated by the wide use of the Weibull distribution in practice, and also for the fact that the generalization provides a continuous crossover towards cases with different shapes. The new distribution is important since it contains as special sub-models some widely-known distributions, such as the generalized modified Weibull, beta Weibull, exponentiated Weibull, beta exponential, modified Weibull and Weibull distributions, among several others. It also provides more flexibility to analyse complex real data. Various mathematical properties of this distribution are derived, including its moments and moment generating function. We examine the asymptotic distributions of the extreme values. Explicit expressions are also derived for the chf, mean deviations, Bonferroni and Lorenz curves, reliability and entropies. The estimation of parameters is approached by two methods: moments and maximum likelihood. We compare by simulation the performances of the estimates from these methods. We obtain the expected information matrix. Two applications are presented to illustrate the proposed distribution.

The exponentiated generalized gamma distribution with application to lifetime data

A four-parameter extension of the generalized gamma distribution capable of modelling a bathtub-shaped hazard rate function is defined and studied. The beauty and importance of this distribution lies in its ability to model monotone and non-monotone failure rate functions, which are quite common in lifetime data analysis and reliability. The new distribution has a number of well-known lifetime special sub-models, such as the exponentiated Weibull, exponentiated generalized half-normal, exponentiated gamma and generalized Rayleigh, among others. We derive two infinite sum representations for its moments. We calculate the density of the order statistics and two expansions for their moments. The method of maximum likelihood is used for estimating the model parameters and the observed information matrix is obtained. Finally, a real data set from the medical area is analysed.

Evaluation of FAO Penman-Monteith and alternative methods for estimating reference evapotranspiration with missing data in Southern Ontario, Canada

Grass reference evapotranspiration (ETo) is an important agrometeorological parameter for climatological and hydrological studies, as well as for irrigation planning and management. There are several methods to estimate ETo, but their performance in different environments is diverse, since all of them have some empirical background. The FAO Penman-Monteith (FAD PM) method has been considered as a universal standard to estimate ETo for more than a decade. This method considers many parameters related to the evapotranspiration process: net radiation (Rn), air temperature (7), vapor pressure deficit (Delta e), and wind speed (U); and has presented very good results when compared to data from lysimeters Populated with short grass or alfalfa. In some conditions, the use of the FAO PM method is restricted by the lack of input variables. In these cases, when data are missing, the option is to calculate ETo by the FAD PM method using estimated input variables, as recommended by FAD Irrigation and Drainage Paper 56. Based on that, the objective of this study was to evaluate the performance of the FAO PM method to estimate ETo when Rn, Delta e, and U data are missing, in Southern Ontario, Canada. Other alternative methods were also tested for the region: Priestley-Taylor, Hargreaves, and Thornthwaite. Data from 12 locations across Southern Ontario, Canada, were used to compare ETo estimated by the FAD PM method with a complete data set and with missing data. The alternative ETo equations were also tested and calibrated for each location. When relative humidity (RH) and U data were missing, the FAD PM method was still a very good option for estimating ETo for Southern Ontario, with RMSE smaller than 0.53 mm day(-1). For these cases, U data were replaced by the normal values for the region and Delta e was estimated from temperature data. The Priestley-Taylor method was also a good option for estimating ETo when U and Delta e data were missing, mainly when calibrated locally (RMSE = 0.40 mm day(-1)). When Rn was missing, the FAD PM method was not good enough for estimating ETo, with RMSE increasing to 0.79 mm day(-1). When only T data were available, adjusted Hargreaves and modified Thornthwaite methods were better options to estimate ETo than the FAO) PM method, since RMSEs from these methods, respectively 0.79 and 0.83 mm day(-1), were significantly smaller than that obtained by FAO PM (RMSE = 1.12 mm day(-1). (C) 2009 Elsevier B.V. All rights reserved.

Definition of priority areas for forest conservation through the ordered weighted averaging method

The general objective of this study was to evaluate the ordered weighted averaging (OWA) method, integrated to a geographic information systems (GIS), in the definition of priority areas for forest conservation in a Brazilian river basin, aiming at to increase the regional biodiversity. We demonstrated how one could obtain a range of alternatives by applying OWA, including the one obtained by the weighted linear combination method and, also the use of the analytic hierarchy process (AHP) to structure the decision problem and to assign the importance to each criterion. The criteria considered important to this study were: proximity to forest patches; proximity among forest patches with larger core area; proximity to surface water; distance from roads: distance from urban areas; and vulnerability to erosion. OWA requires two sets of criteria weights: the weights of relative criterion importance and the order weights. Thus, Participatory Technique was used to define the criteria set and the criterion importance (based in AHP). In order to obtain the second set of weights we considered the influence of each criterion, as well as the importance of each one, on this decision-making process. The sensitivity analysis indicated coherence among the criterion importance weights, the order weights, and the solution. According to this analysis, only the proximity to surface water criterion is not important to identify priority areas for forest conservation. Finally, we can highlight that the OWA method is flexible, easy to be implemented and, mainly, it facilitates a better understanding of the alternative land-use suitability patterns. (C) 2008 Elsevier B.V. All rights reserved.

Genetic potential of a maize population from Southern Brazil for the modified convergent-divergent selection scheme

Maize (Zea mays L.) is a very important cereal to world-wide economy which is also true for Brazil, particularly in the South region. Grain yield and plant height have been chosen as important criteria by breeders and farmers from Santa Catarina State (SC), Brazil. The objective of this work was to estimate genetic-statistic parameters associated with genetic gain for grain yield and plant height, in the first cycle of convergent-divergent half-sib selection in a maize population (MPA1) cultivated by farmers within the municipality of Anchieta (SC). Three experiments were carried out in different small farms at Anchieta using low external agronomic inputs; each experiment represented independent samples of half-sib families, which were evaluated in randomized complete blocks with three replications per location. Significant differences among half-sib families were observed for both variables in all experiments. The expected responses to truncated selection of the 25% better families in each experiment were 5.1, 5.8 and 5.2% for reducing plant height and 3.9, 5.7 and 5.0% for increasing grain yield, respectively. The magnitudes of genetic-statistic parameters estimated evidenced that the composite population MPA1 exhibits enough genetic variability to be used in cyclical process of recurrent selection. There were evidences that the genetic structure of the base population MPA1, as indicated by its genetic variability, may lead to expressive changes in the traits under selection, even under low selection pressure.

Genetic Diversity and a PCR-Based Method for Xanthomonas axonopodis Detection in Passion Fruit

Xanthomonas axonopodis pv. passiflorae causes bacterial spot in passion fruit. It attacks the purple and yellow passion fruit as well as the sweet passion fruit. The diversity of 87 isolates of pv. passiflorae collected from across 22 fruit orchards in Brazil was evaluated using molecular profiles and statistical procedures, including an unweighted pair-group method with arithmetical averages-based dendrogram, analysis of molecular variance (AMOVA), and an assigning test that provides information on genetic structure at the population level. Isolates from another eight pathovars were included in the molecular analyses and all were shown to have a distinct repetitive sequence-based polymerase chain reaction profile. Amplified fragment length polymorphism technique revealed considerable diversity among isolates of pv. passiflorae, and AMOVA showed that most of the variance (49.4%) was due to differences between localities. Cluster analysis revealed that most genotypic clusters were homogeneous and that variance was associated primarily with geographic origin. The disease adversely affects fruit production and may kill infected plants. A method for rapid diagnosis of the pathogen, even before the disease symptoms become evident, has value for producers. Here, a set of primers (Xapas) was designed by exploiting a single-nucleotide polymorphism between the sequences of the intergenic 16S-23S rRNA spacer region of the pathovars. Xapas was shown to effectively detect all pv. passiflorae isolates and is recommended for disease diagnosis in passion fruit orchards.

Particle size and concentration of poly(epsilon-caprolactone) and adipate modified starch blend on mineralization in soils with differing textures

The objective of this study was to evaluate the effect of particle size and concentration of poly(F.-caprolactone) and adipate modified starch blend on mineralization in soils with differing textures, comparing it with polyethylene under the same experimental conditions. Two soil types were used: a Kandiudalfic Eutrudox with a clayey texture and an Arenic Hapludult with a sandy texture. The two different plastic specimens were incorporated in the form of plastic films with three increasing particle sizes and six doses, from 0 to 2.5 mg C g(-1) soil. Each plastic dose was incorporated into 200 g of soil placed in a hermetically closed jar at 28 degrees C, and incubated for a 120-day period to determine CO(2) evolution. Once again it was confirmed that polyethylene is almost non-biodegradable, in contrast to PCL/S, which can be defined as a biodegradable material. Soil texture affected the mineralization kinetics of the plastic specimens, with higher values for the clayey soil. No changes in soil microbial biomass-C or -N were observed by adding polyethylene and PCL/S to the soil. Also, no significant differences were observed on seed emergence and development of rice seedlings (Oryza sativa L.) in plastic modified soil. (C) 2009 Elsevier Ltd. All rights reserved.

ADAPTABILITY AND STABILITY OF SOYBEAN GENOTYPES UNDER DIFFERENT TIMES OF SOWING

This study aimed to evaluate the average behavior, the genotype x environment (GxE), adaptability and stability of seven soybean cultivars at three sowing dates in Uberlandia-MG. The tests were conducted at Capim Branco Farm, belonging to the Federal University of Uberlandia. Sowing was held on october 29 (1st season), november 24 (2nd season) and december 17 (3rd season) 2007. The experimental design was a randomized, seven genotypes (UFUS Xavante, UFUS Riqueza, UFUS Guarani, UFUS Milionaria, Msoy 8001, Msoy 8411 and Msoy 8914) with three replications in each of three sowing dates. Means were compared by Tukey test at 5% probability. Analysis of adaptability and phenotypic stability of genotypes was performed using the Eberhart and Russell (1966), Lin and Binns (1988) modified by Carneiro (1998) and centroid (NASCIMENTO et al., 2009). For grain yield, the cultivar UFUS Xavante was classified as specific adaptability to environment and high stability. The other cultivars were classified as being of general adaptability. For oil content, the cultivars Msoy 8914 and UFUS Xavante behaved as high stability and was classified as having high adaptability. For the character content of protein, all cultivars behaved as wide adaptability and low stability.

Effectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection trials

In stored grains, smaller depositions and great variation with respect to theoretical insecticide doses are frequently found. The objective of this work was to study the effectiveness of the standard method (ISO 5682/1-1996) employed to evaluate hydraulic nozzles used in stored corn and wheat grain protection experiments. The transversal volumetric distribution and droplet spectrum of a model TJ-60 8002EVS nozzle were determined in order to calibrate a spraying system for an application rate of 5 L/t and to obtain theoretical concentrations of 10 and 0.5 mg/kg of fenitrothion and esfenvalerate, respectively. After treatment, the corn and wheat grains were processed and deposition was analyzed by gas chromatography. The type of grain did not have any influence on insecticide deposition and was dependent upon insecticide only. The insecticide deposits on the grains only reached 42.1 and 38.2% of the intended theoretical values for fenitrothion and esfenvalerate concentrations, respectively. These results demonstrate the ineffectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection experiments.

Method development and optimization for the determination of selenium in bean and soil samples using hydride generation electrothermal atomic absorption spectrometry

The present investigation is the first part of an initiative to prepare a regional map of the natural abundance of selenium in various areas of Brazil, based on the analysis of bean and soil samples. Continuous-flow hydride generation electrothermal atomic absorption spectrometry (HG-ET AAS) with in situ trapping on an iridium-coated graphite tube has been chosen because of the high sensitivity and relative simplicity. The microwave-assisted acid digestion for bean and soil samples was tested for complete recovery of inorganic and organic selenium compounds (selenomethionine). The reduction of Se(VI) to Se(IV) was optimized in order to guarantee that there is no back-oxidation, which is of importance when digested samples are not analyzed immediately after the reduction step. The limits of detection and quantification of the method were 30 ng L(-1) Se and 101 ng L(-1) Se, respectively, corresponding to about 3 ng g(-1) and 10 ng g(-1), respectively, in the solid samples, considering a typical dilution factor of 100 for the digestion process. The results obtained for two certified food reference materials (CRM), soybean and rice, and for a soil and sediment CRM confirmed the validity of the investigated method. The selenium content found in a number of selected bean samples varied between 5.5 +/- 0.4 ng g(-1) and 1726 +/- 55 ng g(-1), and that in soil samples varied between 113 +/- 6.5 ng g(-1) and 1692 +/- 21 ng g(-1). (C) 2011 Elsevier B.V. All rights reserved.

Validated method for the quantification of artepillin-C in Brazilian propolis

Brazilian propolis contains several phenolic compounds among which 5 diprenyl-4-hydroxycinnamic acid (artepillin-C) is commonly found in areas where flora is rich in Baccharis species. The quantification of artepillin-C has become an important factor as an indicator of Brazilian propolis quality and the compound may be used as a chemical marker for quality control in exportating green propolis. This work was to validate the method and evaluate the content of artepillin-C from 33 samples collected in different Brazilian regions. The method used was HPLC with UV-vis detection and a reversed-phase C-18 Column. The validation parameters studied were: linearity, accuracy, precision, quantification and detection limits. The results obtained were: detection limit = 0.0036 mu g/mL, quantification limit = 0.012 mu g/mL, accuracy = 0.0064 and 0.078, recovery 98-102%. Artepillin-C content varied from 0 to 11% depending on the geographical origin. Propolis from the southeast region presented the highest level of artepillin-C (5.0-11.0%). Whist that from the northeast region did not show any artepillin-C. Copyright (C) 2008 John Wiley & Sons, Ltd.

Enzymatic-spectrophotometric determination of paraquat in urine samples: A method based on its toxic mechanism

Paraquat is a broad-spectrum contact herbicide that has been encountered worldwide in several cases of accidental, homicidal, and suicidal poisonings. The pulmonary toxicity of this compound is related to the depletion of NADPH in the pneumocytes, which is continuously consumed by the reduction/oxidation of paraquat and reductase enzyme systems in the presence of O(2) (redox cycling). Based on this mechanism, an enzymatic-spectrophotometric method was developed for the determination of paraquat in urine samples. The velocity of NADPH consumption was monitored at 340 nm, every 10 s during 15 min. The velocity of NADPH oxidation correlated with the paraquat levels found in samples. The enzymatic-spectrophotometric method showed to be sensitive, making possible the detection of paraquat in urine samples at concentrations as low as 0.05 mg/L.