893 resultados para variable sample size
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A rapid and economical method is described for the determination of deltamethrin in wheat, rice, peanuts and corn. It is based on simultaneous extraction and clean-up on a column packed with alumina and silica gel using n-hexane-ethyl ether (8:2, v/v), followed by a derivatization step and gas-chromatographic analysis. Recoveries from fortified cereal and peanut samples were determined at four concentration levels and ranged from 73 to 109%. The detection limits were 0.01 to 0.03 mg/ kg. This method simplifies the traditional procedures in terms of sample size, solvent consumption and analysis time. © Springer-Verlag 1998.
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We develop a general model for adaptive c, np, u and p control charts in which one, two or three design parameters (sample size, sampling interval and control limit width) switch between two values, according to the most recent process information. For a given in-control average sampling rate and a given false alarm rate, the adaptive chart detects changes in the process much faster than a chart with fixed parameters. Moreover, this study also offers general guidance on how to choose an effective design.
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Background: Patients with fixed orthodontic appliances often experience an absolute increase in the number of Streptococci mutans colony-forming units (cfu). The aim of this investigation was to study the development of biofilm and S. mutans cfu in connection with stainless steel ligatures and elastomeric rings in orthodontic patients treated with and without 0.4% stannous fluoride gel (SFG). Material: Forty-seven patients were divided into 2 groups: those treated with 0.4% SFG for 4 minutes (experimental) and those without 0.4% SFG (control). In each patient, elastomeric rings were used for ligation on 1 side of the dental arch midline, and stainless steel ligatures were used on the opposite side. Saliva samples were collected before and after appliance placement. At 15 and 30 days after appliance placement, biofilm samples from the stainless steel ligatures and the elastomeric rings were collected and subjected to microbiologic procedures and scanning electron microscopy (SEM) analysis. Results: The numbers of S. mutans cfu in the saliva and biofilm were not statistically different between the teeth fitted with elastomeric rings and stainless steel ligatures, or between the experimental and control groups. SEM analysis showed biofilm formation on both ligature ties. Conclusions: Topical application of 0.4% SFG in orthodontic patients with elastomeric rings or stainless steel ligatures does not cause a significant decrease in S. mutans cfu in the saliva and biofilm. Copyright © 2005 by the American Association of Orthodontists.
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Autism spectrum disorders are severe psychiatric diseases commonly identified in the population. They are diagnosed during childhood and the etiology has been much debated due to their variations and complexity. Onset is early and characterized as communication and social interaction disorders and as repetitive and stereotyped behavior. Austistic disorders may occur together with various genetic and chromosomal diseases. Several chromosomal regions and genes are implicated in the predisposition for these diseases, in particular those with products expressed in the central nervous system. There are reports of autistic and mentally handicapped patients with submicroscopic subtelomeric alterations at the distal end of the long arm of chromosome 2. Additionally, there is evidence that alterations at 2q37 cause brain malformations that result in the autistic phenotype. These alterations are very small and not identified by routine cytogenetics to which patients are normally submitted, which may result in an underestimation of the diagnosis. This study aimed at evaluating the 2q37 region in patients with autistic disorders. Twenty patients were studied utilizing the fluorescence in situ hybridization technique with a specific probe for 2q37. All of them were also studied by the GTC banding technique to identify possible chromosomal diseases. No alterations were observed in the 2q37 region of the individuals studied, and no patient presented chromosomal diseases. This result may be due to the small sample size analyzed. The introduction of routine analysis of the 2q37 region for patients with autistic disorders depends on further studies. ©FUNPEC-RP.
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The epidemiological surveys are important to the deployment, implementation and evaluation of projects and health actions in a community. The planning, goals, samples, team training/calibration, carrying out and publication of results are extremely important in the epidemiological surveys. Thus, the care with the sample and statistical analysis is fundamental for the results to be consistent and trustworthy in order to be able to be inferred for all the population. The aims of this study is to investigate the statistical methodology used in papers on dental caries epidemiological surveys published from 1960 to 2001. A bibliographical survey was carried out in BBO, MEDLINE and SCIELO databases. The papers found were analyzed with regards to the statistical methodology applied in the whole study, from the sampling to the tabling of data. Most studies (72.6%) only presented the number of elements that composed the sample, without explaining the planning involved in obtaining it.
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Includes bibliography
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Background: Cardiovascular disease is the leading cause of death in Brazil, and hypertension is its major risk factor. The benefit of its drug treatment to prevent major cardiovascular events was consistently demonstrated. Angiotensin-receptor blockers (ARB) have been the preferential drugs in the management of hypertension worldwide, despite the absence of any consistent evidence of advantage over older agents, and the concern that they may be associated with lower renal protection and risk for cancer. Diuretics are as efficacious as other agents, are well tolerated, have longer duration of action and low cost, but have been scarcely compared with ARBs. A study comparing diuretic and ARB is therefore warranted.Methods/design: This is a randomized, double-blind, clinical trial, comparing the association of chlorthalidone and amiloride with losartan as first drug option in patients aged 30 to 70 years, with stage I hypertension. The primary outcomes will be variation of blood pressure by time, adverse events and development or worsening of microalbuminuria and of left ventricular hypertrophy in the EKG. The secondary outcomes will be fatal or non-fatal cardiovascular events: myocardial infarction, stroke, heart failure, evidence of new subclinical atherosclerosis and sudden death. The study will last 18 months. The sample size will be of 1200 participants for group in order to confer enough power to test for all primary outcomes. The project was approved by the Ethics committee of each participating institution.Discussion: The putative pleiotropic effects of ARB agents, particularly renal protection, have been disputed, and they have been scarcely compared with diuretics in large clinical trials, despite that they have been at least as efficacious as newer agents in managing hypertension. Even if the null hypothesis is not rejected, the information will be useful for health care policy to treat hypertension in Brazil. Clinical trials registration number: ClinicalTrials.gov: NCT00971165. © 2011 Fuchs et al; licensee BioMed Central Ltd.
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Background: Blood pressure (BP) within pre-hypertensive levels confers higher cardiovascular risk and is an intermediate stage for full hypertension, which develops in an annual rate of 7 out of 100 individuals with 40 to 50 years of age. Non-drug interventions to prevent hypertension have had low effectiveness. In individuals with previous cardiovascular disease or diabetes, the use of BP-lowering agents reduces the incidence of major cardiovascular events. In the absence of higher baseline risk, the use of BP agents reduces the incidence of hypertension. The PREVER-prevention trial aims to investigate the efficacy, safety and feasibility of a population-based intervention to prevent the incidence of hypertension and the development of target-organ damage.Methods: This is a randomized, double-blind, placebo-controlled clinical trial, with participants aged 30 to 70 years, with pre-hypertension. The trial arms will be chlorthalidone 12.5 mg plus amiloride 2.5 mg or identical placebo. The primary outcomes will be the incidence of hypertension, adverse events and development or worsening of microalbuminuria and of left ventricular hypertrophy in the EKG. The secondary outcomes will be fatal or non-fatal cardiovascular events: myocardial infarction, stroke, heart failure, evidence of new sub-clinical atherosclerosis, and sudden death. The study will last 18 months. The sample size was calculated on the basis of an incidence of hypertension of 14% in the control group, a size effect of 40%, power of 85% and P alpha of 5%, resulting in 625 participants per group. The project was approved by the Ethics committee of each participating institution.Discussion: The early use of blood pressure-lowering drugs, particularly diuretics, which act on the main mechanism of blood pressure rising with age, may prevent cardiovascular events and the incidence of hypertension in individuals with hypertension. If this intervention shows to be effective and safe in a population-based perspective, it could be the basis for an innovative public health program to prevent hypertension in Brazil.Trial Registration: Clinical Trials NCT00970931. © 2011 Fuchs et al; licensee BioMed Central Ltd.
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Objective: Evaluate the legal actions and behavior in the doctor/patient relationship, used by dental surgeons practicing orthodontics. Methods: The population sample of the present study consisted of dental surgeons, active in the field of orthodontics, and registered with Dental Press Publishing Company - Maringá/PR, Brazil, with a total sample size of 525 professionals. The research was conducted using a 17-question survey forwarded to these professionals. Results and Conclusions: The majority of participants in our study are specialized in orthodontics; 75% of professionals use some sort of contract at the office/clinic; 73.7% of professionals periodically request maintenance X-rays; a large percentage of professionals (58.9%) keep patient records on file for life. The interviewed professionals demonstrate good knowledge of the Brazilian Code of Ethics in Dentistry, especially of Chapter XIV - on Communication.
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This study aimed to analyze how the prevalence and the distribution of dental caries influence the sample size in epidemiological surveys, and how much are the costs. Secondary data of oral health surveys in 12-year-old schoolchildren from Bauru in 1976, 1984, 1990, 1994, and 2001, and from Piracicaba in 2001 and 2005 were studied. Sample sizes were estimated taking into account the mean DMFT and standard deviation of each survey, establishing sampling errors of 1%, 2%, 5%, and 10%. Costs were estimated considering permanent material, consumption material and human resources. The sample size in both towns needed to be increased, ranging from 119 in 1976 to 1,118 in 2001 in Bauru, and from 954 in 2001 to 1,252 in 2005 in Piracicaba, when a sampling error of 10% was considered. The cost of dental caries surveys was verified considering different sampling errors. This cost depends on how acceptable is the margin of difference between the true mean and the one found in the survey. In conclusion, the reduction in the prevalence of dental caries has determined the need for increase in sample size and in costs for conducting the surveys.
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Anthropogenic changes in the reproductive population density can affect the mating system and result in an increase in selfing and correlated matings. This study investigated the mating system in small fragmented populations of the insect pollinated tropical tree species Copaifera langsdorffii, using microsatellite loci and the mixed and correlated mating models. Open-pollinated seeds were collected from 15 seed-trees located in a small forest fragment (4.8 ha), denominated Bosque and from 14 other seed-trees located in other small forest fragments of the north-western region of São Paulo State. No significant differences were observed between the seed-trees from Bosque (tm=0.933±0.028) and other fragments (tm=0.971±0.032), although these estimates were significantly different from 1.0, suggesting that selfing was occurring. Differences between multilocus and unilocus outcrossing rate were significantly high in both seed-trees of Bosque (tm -ts=0.478±0.05) and other forest fragments (tm -ts=0.475±0.018), suggesting a spatial genetic structure in those stands. The results also showed high rates of correlated mating in the samples, indicating that a good part of the offspring were full-sibs. As a consequence of selfing, mating among relatives and correlated matings, the coancestry within families was equally high in the seed-trees of Bosque ((Θ=0.237) and in the seed-trees of the other forest fragments (Θ=0.241) and the effective population size was lower than expected in panmitic populations (Ne<4). The results were discussed, focusing on the sample size of seed-trees to collect seeds for genetic conservation and enviromental reforestation.
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Newborn infants exposed to preeclampsia (PE) present increased short-term morbidity, mainly respiratory diseases such as respiratory distress syndrome and bronchopulmonary dysplasia. Gastrointestinal problems are also frequent, although a higher risk of necrotizing enterocolitis has not been confirmed. These problems could be related not just to PE itself but also to prematurity or intrauterine growth restriction, which frequently occur in this maternal disease. Other findings, however, seem to be due to the direct effect of the maternal disease; these findings include an increased frequency of neutropenia and thrombocytopenia and a lower incidence of cerebral disorders, such as periventricularintraventricular hemorrhage and cerebral palsy. The evaluation of long-term outcome shows increasing evidence that PE has important implications for the future health of the mother and her child, suggesting that PE is not a simple gestational disorder but a clinical syndrome with an unclear etiology, a genetic component, and a complex pathophysiology. This syndrome involves important maternal and fetal vascular alterations that can persist and cause diseases in later life. The divergence in results on outcomes for children exposed to PE could, in part, be due to methodological differences in the studies, most of which are retrospective case-control studies. Better evidence on prognosis is obtained from cohort studies. Even in the cohort studies, differences in patient characteristics and severity of maternal disease, as well as sample size, follow-up time, and main outcome measures certainly contribute to the variability in results reported in the literature. © 2012 by the American Academy of Pediatrics. All rights reserved.
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Intense selective pressures applied over short evolutionary time have resulted in homogeneity within, but substantial variation among, horse breeds. Utilizing this population structure, 744 individuals from 33 breeds, and a 54,000 SNP genotyping array, breed-specific targets of selection were identified using an FST-based statistic calculated in 500-kb windows across the genome. A 5.5-Mb region of ECA18, in which the myostatin (MSTN) gene was centered, contained the highest signature of selection in both the Paint and Quarter Horse. Gene sequencing and histological analysis of gluteal muscle biopsies showed a promoter variant and intronic SNP of MSTN were each significantly associated with higher Type 2B and lower Type 1 muscle fiber proportions in the Quarter Horse, demonstrating a functional consequence of selection at this locus. Signatures of selection on ECA23 in all gaited breeds in the sample led to the identification of a shared, 186-kb haplotype including two doublesex related mab transcription factor genes (DMRT2 and 3). The recent identification of a DMRT3 mutation within this haplotype, which appears necessary for the ability to perform alternative gaits, provides further evidence for selection at this locus. Finally, putative loci for the determination of size were identified in the draft breeds and the Miniature horse on ECA11, as well as when signatures of selection surrounding candidate genes at other loci were examined. This work provides further evidence of the importance of MSTN in racing breeds, provides strong evidence for selection upon gait and size, and illustrates the potential for population-based techniques to find genomic regions driving important phenotypes in the modern horse. © 2013 Petersen et al.
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Purpose: Small renal masses are increasingly being discovered incidentally on imaging for another reason. The standard of care of these masses involves excision by open or laparoscopic techniques. Recently, ablative techniques, such as radiofrequency ablation (RFA) and cryoablation, have taken a more prominent role in the treatment algorithm of these masses. We evaluate the effectiveness and safety of cryoablation to treat renal tumours. Methods: A review of the literature was conducted. There was no language restriction. Studies were obtained from the following sources: the Cochrane Library, PUBMED, EMBASE and LILACS. Results: There was no clinical trial identified in the literature. Thus, we described the results from 23 case series and retrospective studies with a reasonable sample size (number of reported patients in each study ≥30), with a total of 2104 analyzed tumours from 2038 patients. There was wide variability in the outcomes reported, but success rates were generally good. Follow-up was generally short, but some series reported outcomes at 5 years. The most common complications reported were hemorrhage (some of the patients requiring transfusion), perinephric hematoma and urine leaks. Conclusion: Cryoablation presents a feasible treatment for patients with small renal masses. Only short-term data are available and, as such, meaningful conclusions regarding long-term cancer control cannot be made. More rigorous studies are needed. © 2013 Canadian Urological Association.
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The objective of the present study was to develop a sequential sampling plan for the decision-making process to control Tenuipalpus heveae Baker (Acari: Tenuipalpidae), an important pest of the rubber tree crop. The experimental area was represented by 1,000 plants of the RRIM 600 clone divided in 100 plots with 10 plants each. Leaves were collected and the number of mites determined under laboratory conditions. The sequential sampling plan was developed in accordance with the Sequential Test Likelihood Ratio. The value 0.10 was pre-established for α and β representing type I and type II errors, respectively. The level of control adopted was six mites per 12 cm2. The operating characteristic curve and the curve of maximum expected sample were determined. Two lines were generated: the upper one, when the condition for chemical control is recommended (S1 = 23.3080 + 2.1972); and the lower, when chemical control is not recommended (S0 = -23.3080 + 2.1972). Sample size for the decision-making process to control T. heveae requires 6 to 18 plants. © 2013 Sociedade Entomológica do Brasil.