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Statistical tests on the distribution of the number of chiasmata per chromosome, collected from literatures, showed that they can be approximated by binomial distributions with one obligatory chiasma, i.e., B(N-1, p). N is proportional to the average number of chiasmata, while p is nearly constant for the species tested.
Green's sequential sampling plan is widely used in applied entomology. Green's equation can be used to construct sampling stop charts, and a crop can then be surveyed using a simple random sampling (SRS) approach. In practice, however, crops are rarely surveyed according to SRS. Rather, some type of hierarchical design is usually used, such as cluster sampling, where sampling units form distinct groups. This article explains how to make adjustments to sampling plans that intend to use cluster sampling, a commonly used hierarchical design, rather than SRS. The methodologies are illustrated using diamondback moth, Plutella xylostella (L.), a pest of Brassica crops, as an example.
Cytogenetic effect of cyclophosphamide in cultured human lymphocytes after its activation in C57BL/6 mice in vivo was investigated. Cyclophosphamide was injected intraperitoneally in mice for 30 min. at doses of 200, 400, 600, 800 and 1000 mg/kg. Blood serum with activated metabolites of cyclophosphamide was added to human lymphocyte culture. The dependence of the part of aberrant metaphases on the concentration of cyclophosphamide after the activation can be presented as equation rho==1-e-(KC+alpha)2 and the total number of breaks as X=e(KC+alpha)2-1, where rho is a part of aberrant metaphases, X is a number of breaks of chromosomes per cell, C is the concentration, K and alpha are coefficients. The part of chromatid breaks from the total number of chromosome damages is constant for all concentrations and the comprises on the average 79,11%. Only the chromatid type of exchanges are observed. Distribution of chromosome breaks in cells corresponds to geometrical, but not to Poisson's distribution. Cyclophosphamide belongs to the group of one-sited mutagens in its cytogenetic chatacteristics. The alkylating activity of cyclophosphamide metabolites, estimated by means of NBP test, increases up to the dose 400 mg/kg and then remains constant for the strain of mice studied, cytogenetic activity increasing. Cyclophosphamide does not produce cytogenetic activity without activation. To test chemical substances for mutagenic activity, it is suggested to activate them in the mouse organism with the following administrating blood serum of these animals with the metabolites of tested (or with primary) substances in the study of their mutagenic activity on human lymphocyte culture.
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Imitation model study evaluated uncertainty in evaluation of rank trend characteristics. The trends describe age-matched oncologic mortality and morbidity. The uncertainty (dispersion and shift) of the evaluation decreases with growing population and trend rank, becomes allowable for population exceeding 100,000.
A recent model for olfactory foraging by procellariiform seabirds suggests that these birds use biogenic sulfur compounds to locate productive areas for foraging in the southern oceans. The present study refines a simple approach to test birds' responses to odors on land and extends our knowledge to a northern species, the Leach's storm-petrel (Oceanodroma leucorhoa). Rather than working at sea, we tested the behavioral response to dimethyl sulfide (DMS) at night in breeding colonies on Kent Island, New Brunswick, Canada. Birds were presented with either 5 ml DMS (100 micro mol l(-1) concentration) or control (water) solutions from a platform 1.5 m in height positioned in a flyway 10 m from a breeding colony. We also tested birds' responses to cod liver oil, a well-established olfactory attractant of procellariiforms foraging at sea. Leach's storm-petrels approached DMS presentations nearly twice as frequently as they approached controls. We next compared the distribution of approaches against a Poisson process to test for evidence of social cueing. We found that approaches to DMS were significantly clustered. By contrast, the distribution of approaches did not depart significantly from a Poisson distribution for either cod liver oil or control presentations. Taken together, these results suggest that Leach's storm-petrels can smell DMS and potentially use it as a foraging cue. The results are consistent with the hypothesis that the detection of biogenic sulfur compounds in combination with other cues assists birds in locating foraging hotspots.
A method of sample size determination for estimation of probabilities based on a test variable is presented. Applications to estimation of sensitivity and specificity of medical tests are the focus of this research, although the methods can be applied to other areas of study such as engineering reliability. Examples are given for determining sample sizes required for the classification of patients with cutaneous lupus erythematosus based on the incidence of several markers. In this example, the test variable is the number of markers present. The methodology employs a weighted average of model-based and non-model-based estimates of the probability with the weights determined by the closeness to or the confidence in the given model. Formulas and charts required for determining sample size are provided for test variables that can be modeled by the binomial, Poisson, or normal distributions, i.e., for the most commonly encountered distributions for counting events (binomial and Poisson) and for measurements (normal). However, the methods given can be applied to any distribution, including multivariate. Especially when relatively small probabilities (the rare events) are being estimated, the techniques provided assistance in safeguarding against undersampling brought on by unwarranted confidence in a test variable distribution and against oversampling required for high accuracy in non-model-based probability estimators.
A method is introduced for computing a Bayesian 95 per cent posterior probability region for vaccine efficacy. This method assumes independent vague gamma prior distributions for the incidence rates on each arm of the trial, and a Poisson likelihood for the counts of incident cases of infection. The approach is similar in spirit to the Bayesian analysis of the binomial risk ratio described by Aitchison and Bacon-Shone. However, the focus of our interest is not on incorporating prior information into the design of trials for efficacy, but rather on evaluating whether or not the Bayesian approach with vague prior information produces comparable results to a frequentist approach. A review of methods for constructing exact and large sample intervals for vaccine efficacy is provided as a framework for comparison. The confidence interval methods are assessed by comparing the size and power of tests of vaccine efficacy in proposed intermediate sized randomized double blinded placebo controlled trials.
To clarify the dynamics of leukocyte delivery to the capillary network we measured leukocyte velocity (Vwbc), leukocyte flux and the intra-arrival times between successive leukocytes in terminal arterioles of the cheekpouch of eight hamsters. The sequences, generated electronically when fluorescent leukocytes passed a fixed point in the arteriole, were analyzed as stochastic point processes. Results showed that six sequences were stationary, and two with a linear trend in Vwbc, were not. Tests performed on the stationary sequences indicated conformity to a renewal process in all cases. Analysis of the distributional and sequential properties of the sequences indicated a good fit to a Poisson process. Overall these results show that leukocyte delivery to the capillary network can be characterized as a Poisson process if Vwbc remains relatively constant, if not, a non-homogeneous Poisson process is a more suitable model, with Vwbc being the explanatory variable. The demonstration of the applicability of these models may lead to a more complete understanding of both the physiological and patho-physiological dynamics of leukocytes within the microvasculature.
This study was designed to test the hypothesis that among unrelated male baboons (Papio cynocephalus anubis) in single-gender social groups there is no significant association between dominance status and allogrooming performance. The hypothesis was tested using behavioral measures obtained by focal animal sampling techniques. The results indicate that unrelated male baboons established well-defined linear dominance hierarchies, formed allogrooming relationships with one another, and exhibited a nonrandom distribution of allogrooming; however, there were no significant relationships between dominance rank and the frequency of allogrooming. We further tested our results by grouping individuals into three dominance status classes (high, middle, and low) and comparing the classes. Analysis of variance demonstrated no significant differences in rates of allogrooming by dominance class. These results suggest that dominance did not account for the variation in observed allogrooming behavior: Dominance status did not appear to determine the frequency with which animals groomed others, the number of grooming partners, or frequency of grooming that any individual received in comparison to that performed. High-ranking animals did not have significantly more grooming partners than low-ranking animals, and there appeared to be little competition within the groups for subordinates to groom high-ranking animals. When age, kinship, and group tenure are controlled, performance and reception of allogrooming are not strongly associated with dominance in single-gender social groups of male anubis baboons.
LMC (local mate competition) was first introduced by W. D. Hamilton to explain extraordinary female-biased sex ratios observed in a variety of insects and mites. In the original model, the population is subdivided into an infinite number of colonies founded by a fixed number of inseminated females producing the same very large number of offspring. The male offspring compete within the colonies to inseminate the female offspring and then these disperse at random to found new colonies. An unbeatable sex ratio strategy is found to be female-biased. In this paper, the effects of having colonies of random size and foundresses producing a random finite number of offspring are considered. The exact evolutionarily stable strategy (ESS) sex ratio is deduced and comparisons with previous approximate or numerical results are made. As the mean or the variance of brood size increases, the ESS sex ratio becomes more female-biased. An increase in the variance of colony size increases the ESS proportion of males when the mean brood size and colony size are both small, but decreases this proportion when the mean brood size or the mean colony size is large.
Choosing the design of a dilution series experiment on the basis of availability of most probable number tables can result in a non-optimal design. Similarly, certain tables and/or rules for declaring dilution series results 'improbable' do not always give optimal decisions. Further, tables of most probable number confidence intervals are not all based on the same assumptions and give different intervals--which should be used? The aim of this article is to draw microbiologists' attention to these issues and to suggest practical solutions.
BACKGROUND: Is cancer related to hypertension and blood pressure? Do antihypertensive drugs promote cancer? Do antihypertensive drugs protect against cancer? We previously analysed the frequency of cardiovascular mortality and morbidity in elderly people who participated in the Swedish Trial in Old Patients with Hypertension 2 (STOP-Hypertension-2). We have also looked at the frequency of cancer in these patients. METHODS: We randomly assigned 6614 elderly patients with hypertension (mean age 76 years, median time of follow-up 5.3 years) to one of three treatment strategies: conventional drugs (diuretics or b-blockers), calcium antagonists, or ACE inhibitors. We matched the patients to the Swedish Cancer Registry and compared our findings with expected values based on age, sex, and calendar-year-specific reference frequencies for the general Swedish population. We also compared the number of cancers between the three treatment groups. FINDINGS: At baseline, 607 (9%) patients had previous malignant disease. Diagnoses were closely similar to the distribution of cancer types that might be seen in elderly patients. During follow-up, there were 625 new cases of cancer in 590 patients. The frequency of cancer did not differ significantly between the treatment strategies, including all cancers and those at individual sites. The standardised incidence ratios (SIRs) for all cancers were also close to unity: 0.92 (95% CI 0.80-1.06) for conventional drugs, 0.96 (0.83-1.10) for calcium antagonists, and 0.99 (0.86-1.13) for ACE inhibitors. INTERPRETATIONS: No difference in cancer risk was seen between patients randomly assigned to conventional drugs, calcium antagonists, or ACE inhibitors. Thus, the general message to the practising physician is that more attention should be given to getting the blood pressure down than to the risk of cancer.
STUDY OBJECTIVE: We describe errors occurring in a busy ED. METHODS: This is a prospective, observational study of reported errors at an academic emergency department (ED) with 100000 annual visits. Trained personnel interviewed all ED staff with direct patient contact, during and at the end of every shift, by using standardized data sheets. RESULTS: One thousand nine hundred thirty-five ED patients registered during the 7-day study period in the summer of 2001. Four hundred error reports were generated, identifying 346 nonduplicative errors (18 per 100 registered patients; 95% confidence interval [CI] 15.9 to 20.0). Forty percent of errors were reported by nurses, 25% by providers, 19% by clerical staff, 13% by technicians and orderlies, and 3% multiple reporters. Errors reported for every 100 hours worked were similar for all groups (5.5; 95% CI 5.2 to 5.9). Errors were categorized as 22% diagnostic studies, 16% administrative procedures, 16% pharmacotherapy, 13% documentation, 12% communication, 11% environmental, and 9% other. Patients involved in errors were more likely to be older (P <.0001) and more likely to have higher visit level intensity (P <.0001) than registered ED patients. Ninety-eight percent of errors did not have a significant adverse outcome. Seven errors (0.36 per 100 registered patients; 95% CI 0.14 to 0.72) were associated with an adverse outcome. CONCLUSION: Reported errors occurred in almost every aspect of emergency care. Ninety-eight percent of errors in the ED do not result in adverse outcomes. System changes need to be implemented to reduce ED errors.
BACKGROUND: Knowledge of circulating serotypes of group B Streptococcus (GBS) is important for formulation of vaccines. There are no Canadian data on the serotype distribution of neonatal GBS isolates. METHODS: Using a retrospective laboratory and health record survey between 1993 and 1994 (before introduction of Canadian prevention guidelines) and prospective active laboratory-based surveillance from 1995 to 1999 of all laboratories in Alberta, we identified 168 cases of invasive neonatal GBS infections including stillbirths among 262,398 total births; 118 of 123 (96%) isolates from 1995 to 1999 were serotyped, and the corresponding neonatal health records were reviewed. RESULTS: The average annual incidence was 0.64 of 1000 total births/year. Of these 95 (57%) had early onset disease (EOD), 15 (9%) were still births and 58 (34%) had late onset disease (LOD). Eighty-one percent of EOD cases were caused by serotypes Ia, Ia/c, Ia/c/R, III, III/R and V, V/R, whereas 81% of LOD cases were caused by serotypes III and III/R. GBS serotypes containing the C protein along with serotypes III and V as a group constituted 91% (107 of 118) of all GBS cases in our population. The most common clinical presentation was bacteremia without focus (74%) followed by meningitis (14%) and pneumonia (12%). During 1995 to 1999, in addition to 13 stillbirths, there were 6 of 64 (9%) neonatal deaths among EOD cases and 1 of 46 (2%) neonatal death among LOD cases. CONCLUSIONS: In this population-based study stillbirths account for a proportion of cases that are not routinely counted and represent a group for which intrapartum antibiotics would likely not be effective, but potentially preventable by vaccination. Inclusion of serotypes Ia, III and V in a conjugate vaccine or serotypes III and V conjugated with the C protein in a GBS vaccine could theoretically provide protection against the majority of GBS invasive disease in Alberta neonates.
In a model for rotating non-Boussinesq convection with mean flow, we identify a regime of spatiotemporal chaos that is based on a hexagonal planform and is sustained by the induced nucleation of dislocations by penta-hepta defects. The probability distribution function for the number of defects deviates substantially from the usually observed Poisson-type distribution. It implies strong correlations between the defects in the form of density-dependent creation and annihilation rates of defects. We extract these rates from the distribution function and also directly from the defect dynamics.
Charged particle multiple scattering distributions may be constructed from individual atomic scattering events on the basis of compound Poisson process (CPP) theory. We present a CPP method for computing multiple scattering transition probability densities from charged particles penetrating compounds and mixtures. Water as a scattering medium provides here an example of the calculation method which is applicable to compounds or mixtures. Electrons are chosen as examples of charged particle beams. The Rutherford single scattering cross section and a partial wave analysis single scattering cross section are chosen as example cross sections. Transition probability densities predicted on the basis of CPP theory can be calculated with great accuracy for the improvement of radiation dose calculations. The advantages of the CPP method are (a) an effective atomic number need not be defined for the scattering medium, (b) it can be applied in both spherical and planar coordinate systems, and (c) it does not require any specific form for the single scattering cross section.
PURPOSE: Noninvasive lesions involving the lobules of the breast are increasingly diagnosed as incidental microscopic findings at the time of lumpectomy or core-needle biopsy. We investigated the incidence rates of invasive breast cancer (IBC) after a diagnosis of lobular carcinoma-in-situ (LCIS) by using Surveillance, Epidemiology, and End Results (SEER) data. PATIENTS AND METHODS: Patients (N = 4,853) having a diagnosis of primary LCIS in the time period of 1973 to 1998 were identified using the SEER Public Use CD-ROM data. The database was then searched for patients with subsequent primary IBC occurrences (n = 350). The clinical and pathologic characteristics of patients with subsequent primary IBCs were compared with the characteristics of patients with primary IBCs attained during the same time period (N = 255,114). RESULTS: The incidence of IBC increased over time from diagnosis of LCIS, with 7.1% +/- 0.5% incidence of IBC at 10 years. IBCs detected after partial mastectomy occurred in either breast (46% ipsilateral and 54% contralateral); however, after mastectomy, most IBCs were contralateral (94.7%). IBCs occurring after LCIS more often represented invasive lobular histology (23.1%) compared with primary IBCs (6.5%). The standardized incidence ratio (the ratio of observed to expected cases) for developing IBC was 2.4 (95% CI, 2.1 to 2.6) adjusted for age and year of diagnosis. CONCLUSION: LCIS is associated with increased risk of subsequent invasive disease, with equal predisposition in either breast. The minimum risk of developing IBC after LCIS is 7.1% at 10 years.