938 resultados para regression ana-lysis


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The broiler rectal temperature (t rectal) is one of the most important physiological responses to classify the animal thermal comfort. Therefore, the aim of this study was to adjust regression models in order to predict the rectal temperature (t rectal) of broiler chickens under different thermal conditions based on age (A) and a meteorological variable (air temperature - t air) or a thermal comfort index (temperature and humidity index -THI or black globe humidity index - BGHI) or a physical quantity enthalpy (H). In addition, through the inversion of these models and the expected t rectal intervals for each age, the comfort limits of t air, THI, BGHI and H for the chicks in the heating phase were determined, aiding in the validation of the equations and the preliminary limits for H. The experimental data used to adjust the mathematical models were collected in two commercial poultry farms, with Cobb chicks, from 1 to 14 days of age. It was possible to predict the t rectal of conditions from the expected t rectal and determine the lower and superior comfort thresholds of broilers satisfactorily by applying the four models adjusted; as well as to invert the models for prediction of the environmental H for the chicks first 14 days of life.

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Singular Value Decomposition (SVD), Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) are some of the mathematical pre- liminaries that are discussed prior to explaining PLS and PCR models. Both PLS and PCR are applied to real spectral data and their di erences and similarities are discussed in this thesis. The challenge lies in establishing the optimum number of components to be included in either of the models but this has been overcome by using various diagnostic tools suggested in this thesis. Correspondence analysis (CA) and PLS were applied to ecological data. The idea of CA was to correlate the macrophytes species and lakes. The di erences between PLS model for ecological data and PLS for spectral data are noted and explained in this thesis. i

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PURPOSE: To evaluate the prevalence of women aged 50 years or more who are sexually active and their self-perception with respect to their sexual lives. Associated factors were also assessed. METHODS: A cross-sectional, population-based, self-reported household survey involving 622 Brazilian women aged 50 years or more. Sociodemographic, clinical, and behavioral factors were evaluated. The sexual life self-perception was classified as very good, good, fair, poor, or very poor. Data were analyzed using the χ² test, Fisher's exact test, and Poisson multiple regression analysis. Prevalence ratios and their 95% confidence intervals were also calculated. RESULTS: Of the women in this sample, 228 (36.7%) reported having a sexual life and, of these, 53.5% classified it as very good or good, while 46.5% considered it fair, poor, or very poor. The bivariate analysis indicated that being postmenopausal (p=0.025) and using natural remedies to treat the menopause (p=0.035) were factors associated with the woman classifying their sexual lives as fair, poor, or very poor. Multiple regression analysis showed that more women who had used or were currently using natural remedies for the menopause scored their sexual lives as fair, poor, or very poor. CONCLUSIONS: More than half the women aged 50 years or more in this study were not sexually active. A poorer sexual life self-perception was associated with the use of natural remedies to treat menopausal symptoms. This may indicate a need to improve the way in which these women are evaluated and treated. Women's assessment of their own sexual lives may prove a useful tool in clinical practice.

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PURPOSE:To evaluate factors associated with hypertension in Brazilian women of 50 years of age or more.METHODS:A cross-sectional population based study using self-reports. A total of 622 women were included. The association between sociodemographic, clinical and behavioral factors and the woman's age at the onset of hypertension was evaluated. Data were analyzed according to cumulative continuation rates without hypertension, using the life-table method and considering annual intervals. Next, a Cox multiple regression analysis model was adjusted to analyze the occurrence rates of hypertension according to various predictor variables. Significance level was pre-established at 5% (95% confidence level) and the sampling plan (primary sampling unit) was taken into consideration.RESULTS:Median age at onset of hypertension was 64.3 years. Cumulative continuation rate without hypertension at 90 years was 20%. Higher body mass index (BMI) at 20–30 years of age was associated with a higher cumulative occurrence rate of hypertension over time (coefficient=0.078; p<0.001). Being white was associated with a lower cumulative occurrence rate of hypertension over time (coefficient= -0.439; p=0.003), while smoking >15 cigarettes/day was associated with a higher rate over time (coefficient=0.485; p=0.004).CONCLUSION:The results of the present study highlight the importance of weight control in young adulthood and of avoiding smoking in preventing hypertension in women aged ≥50 years.

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The aim of this study was evaluate the risk factors for Mycobacterium avium subsp. paratuberculosis (Map) seroprevalence in sheep in the North of Portugal. The effects on seroprevalence of several variables such as individual characteristics, management practices, farm characteristics, animal health, and available veterinary services were evaluated. This information was then used in a multivariable logistic regression model in order to identify risk factors for Map seropositivity. Univariable analysis was used to screen the variables used in the logistic regression model. Variables that showed p values of <0.15 were retained for the multivariable analysis. Fifteen variables were associated with paratuberculosis in univariable analysis. The multivariable logistic regression model identified a number of variables as risk factors for seropositivity like sheep pure local and/or a cross of a local breed (OR=2.02), herd size with 31-60 head (OR=2.14), culling during the Spring-Summer season (OR=1.69) and the use of an anti-parasitic treatment such as Ivermectin as the only anti-parasitic medication (OR=5.60). Potential risk factors identified in this study support current recommendations for the control of paratuberculosis.

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Bovine genital campylobacteriosis is a common venereal disease of cattle; the prevalence of this disease can be underestimated mostly because of the nature of the etiological agent, the microaerobic Campylobacter fetus subspecies venerealis. The purpose of the current study was to evaluate the utilization of polymerase chain reaction (PCR) in the diagnosis of genital campylobacteriosis in samples obtained from bull prepuce aspirate, cow cervical mucus, and abomasum contents of aborted fetuses, collected into enrichment medium. Five different DNA extraction protocols were tested: thermal extraction, lysis with proteinase K, lysis with guanidine isothiocyanate, lysis with DNAzol, and lysis with hexadecyltrimethylammonium bromide (CTAB). The specificity, sensitivity, and technical application of the PCR assay were also evaluated with clinical samples and compared to bacterial isolation by standard culture. DNA extraction by the CTAB protocol provided better results in PCR, and it was able to detect 63 colony-forming units per ml of C. fetus. Out of 277 clinical samples tested, 68 (24%) were positive for Campylobacter fetus using PCR, while only 8 (2.8%) of the samples were positive by bacterial isolation in solid medium, proving the superiority of the PCR technique when compared to the standard isolation method, and providing evidence for its usefulness as a better screening test in cattle for the diagnosis of bovine genital campylobacteriosis.

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Cardiopulmonary reflexes are activated via changes in cardiac filling pressure (volume-sensitive reflex) and chemical stimulation (chemosensitive reflex). The sensitivity of the cardiopulmonary reflexes to these stimuli is impaired in the spontaneously hypertensive rat (SHR) and other models of hypertension and is thought to be associated with cardiac hypertrophy. The present study investigated whether the sensitivity of the cardiopulmonary reflexes in SHR is restored when cardiac hypertrophy and hypertension are reduced by enalapril treatment. Untreated SHR and WKY rats were fed a normal diet. Another groups of rats were treated with enalapril (10 mg kg-1 day-1, mixed in the diet; SHRE or WKYE) for one month. After treatment, the volume-sensitive reflex was evaluated in each group by determining the decrease in magnitude of the efferent renal sympathetic nerve activity (RSNA) produced by acute isotonic saline volume expansion. Chemoreflex sensitivity was evaluated by examining the bradycardia response elicited by phenyldiguanide administration. Cardiac hypertrophy was determined from the left ventricular/body weight (LV/BW) ratio. Volume expansion produced an attenuated renal sympathoinhibitory response in SHR as compared to WKY rats. As compared to the levels observed in normotensive WKY rats, however, enalapril treatment restored the volume expansion-induced decrease in RSNA in SHRE. SHR with established hypertension had a higher LV/BW ratio (45%) as compared to normotensive WKY rats. With enalapril treatment, the LV/BW ratio was reduced to 19% in SHRE. Finally, the reflex-induced bradycardia response produced by phenyldiguanide was significantly attenuated in SHR compared to WKY rats. Unlike the effects on the volume reflex, the sensitivity of the cardiac chemosensitive reflex to phenyldiguanide was not restored by enalapril treatment in SHRE. Taken together, these results indicate that the impairment of the volume-sensitive, but not the chemosensitive, reflex can be restored by treatment of SHR with enalapril. It is possible that by augmenting the gain of the volume-sensitive reflex control of RSNA, enalapril contributed to the reversal of cardiac hypertrophy and normalization of arterial blood pressure in SHR.

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Streptokinase, a 47-kDa protein isolated and secreted by most group A, C and G ß-hemolytic streptococci, interacts with and activates human protein plasminogen to form an active complex capable of converting other plasminogen molecules to plasmin. Our objective was to compare five streptokinase formulations commercially available in Brazil in terms of their activity in the in vitro tests of euglobulin clot formation and of the hydrolysis of the plasmin-specific substrate S-2251™. Euglobulin lysis time was determined using a 96-well microtiter plate. Initially, human thrombin (10 IU/ml) and streptokinase were placed in individual wells, clot formation was initiated by the addition of plasma euglobulin, and turbidity was measured at 340 nm every 30 s. In the second assay, plasminogen activation was measured using the plasmin-specific substrate S-2251™. Streptase™ was used as the reference formulation because it presented the strongest fibrinolytic activity in the euglobulin lysis test. The Unitinase™ and Solustrep™ formulations were the weakest, showing about 50% activity compared to the reference formulation. All streptokinases tested activated plasminogen but significant differences were observed. In terms of total S-2251™ activity per vial, Streptase™ (75.7 ± 5.0 units) and Streptonase™ (94.7 ± 4.6 units) had the highest activity, while Unitinase™ (31.0 ± 2.4 units) and Strek™ (32.9 ± 3.3 units) had the weakest activity. Solustrep™ (53.3 ± 2.7 units) presented intermediate activity. The variations among the different formulations for both euglobulin lysis test and chromogenic substrate hydrolysis correlated with the SDS-PAGE densitometric results for the amount of 47-kDa protein. These data show that the commercially available clinical streptokinase formulations vary significantly in their in vitro activity. Whether these differences have clinical implications needs to be investigated.

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Dedikaatio: Ericus Falander, Bartholdus Fästing.

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Moisture equilibrium data of mango pulp were determined using the static gravimetric method. Adsorption and desorption isotherms were obtained in the range of 30-70 ºC, to water activities (a w) from 0.02 to 0.97. The application of the GAB model to the experimental results, using direct nonlinear regression analysis, provided agreement between experimental and calculated values. The net isosteric heat of sorption was estimated from equilibrium sorption data, using the Clausius-Clapeyron equation. Isosteric heats of sorption were found to increase with increasing temperature and could be well adjusted by an exponential relationship. The enthalpy-entropy compensation theory was applied to sorption isotherms and plots of deltaH versus deltaS provided the isokinetic temperatures, indicating an enthalpy controlled sorption process.

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Rheological and thermophysical properties were determined for blackberry juice, which was produced from blackberry fruit at 9.1 ± 0.5 °Brix and density of 1.0334 ± 0.0043 g cm-3. The concentration process was performed using a roto evaporator, under vacuum, to obtain concentrated juice at about 60 °Brix. In order to obtain different concentrations, concentrated juice was diluted with distilled water. Rheological measurements were carried out using a Rheotest 2.1 Searle type rheometer. In the tested ranges, the samples behaved as pseudoplastic fluids, and the Power-Law model was satisfactorily fitted to the experimental data. The friction factor was measured for blackberry juice in laminar flow conditions of pseudoplastic behavior. Thermal conductivity, thermal diffusivity and density of blackberry juice at 9.4 to 58.4 °Brix were determined, in triplicate, at 0.5 to 80.8 °C. Polynomial regression was performed to fit experimental data obtaining a good fit. Both temperature and concentration showed a strong influence on thermophysical properties of blackberry juice. Calculated apparent specific heat values varied from 2.416 to 4.300 kJ.kg-1 °C in the studied interval.

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This study aimed to verify the influence of pH and temperature on the lysis of yeast using experimental design. In this study, the enzymatic extract containing β-1,3-glucanase and chitinase, obtained from the micro-organism Moniliophthora perniciosa, was used. The experiment showed that the best conditions for lysis of Pseudozyma sp. (CCMB 306) and Pseudozyma sp. (CCMB 300) by lytic enzyme were pH 4.9 at 37 ºC and pH 3.9 at 26.7 ºC, respectively. The lytic enzyme may be used for obtaining various biotechnology products from yeast.

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Ordered probit regression was used to analyze data of sensory acceptance tests designed to study the effect of brand name on the acceptability of beer samples. Eight different brands of Pilsen beer were evaluated by 101 consumers in two sessions of acceptance tests: blind evaluation and brand information test. Ordered probit regression, although a relatively sophisticated technique compared to others used to analyze sensory data, was chosen to enable the observation of consumers' behavior using graphical interpretations of estimated probabilities plotted against hedonic scales. It can be concluded that brands B, C, and D had a positive effect on the sensory acceptance of the product, whereas brands A, F, G, and H had a negative influence on consumers' evaluation of the samples. On the other hand, brand E had little influence on consumers' assessment.

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This study developed a gluten-free granola and evaluated it during storage with the application of multivariate and regression analysis of the sensory and instrumental parameters. The physicochemical, sensory, and nutritional characteristics of a product containing quinoa, amaranth and linseed were evaluated. The crude protein and lipid contents ranged from 97.49 and 122.72 g kg-1 of food, respectively. The polyunsaturated/saturated, and n-6:n-3 fatty acid ratios ranged from 2.82 and 2.59:1, respectively. Granola had the best alpha-linolenic acid content, nutritional indices in the lipid fraction, and mineral content. There were good hygienic and sanitary conditions during storage; probably due to the low water activity of the formulation, which contributed to inhibit microbial growth. The sensory attributes ranged from 'like very much' to 'like slightly', and the regression models were highly fitted and correlated during the storage period. A reduction in the sensory attribute levels and in the product physical stabilisation was verified by principal component analysis. The use of the affective test acceptance and instrumental analysis combined with statistical methods allowed us to obtain promising results about the characteristics of gluten-free granola.

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Abstract Grape pomace, which is derived from the skin and seeds, is the residue from the production of grape juice and wine. It corresponds to up to 20% of the total volume and it contains a high level of dietary fibers and bioactive compounds. In the Brazilian market, there is no product containing grape pomace as a replacement for conventional wheat flour. Thus, this study aimed to assess the effects of whole-wheat flour and organic Bordeaux grape pomace (Vitis labrusca L.) on the sensory, physicochemical and functional properties of cookies using response surface methodology (RSM). The regression models indicated that the addition of whole-wheat and organic grape pomace decreased (p < 0.0001) the water activity and significantly increased the content of fibers, hardness, brittleness, antioxidant activity and total phenolic content of the cookies. The RSM models presented suitable R2 and R2adj values (> 65% of explained data variability), except for brittleness. The sensory evaluation results revealed that no significant differences (p > 0.05) were observed for the cookie samples, implying that the addition of grape pomace and whole-wheat flour did not negatively affect the preference of cookies.