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PubMed1997

Review of methods for transformation skinfolds data to normality for boys and girls from 7 to 19 years old.

The most popular method to estimate fatness is anthropometry, especially measurement of skinfold thicknesses. However, such kind of data seriously departs from normal distribution. The present study reviews some methods not age or sex dependent for normalizing triceps and subscapular skinfolds data distribution. Material consists 1408 boys and 1390 girls aged 7-19 from Warsaw measured in 1987-88. The following methods were tested: log(x), log(x-c), -1/x, -1/square route of x. Approximation to the normality were judged by means of the Shapiro-Wilks W test. The results indicate that log(x-c) gave the best transformation of triceps skinfold for boys and girls. The best method for subscapular site appeared -1/x for boys and -1/square route of x for girls. The most popular log(x) is not sufficient for correct normalization. Nevertheless, none of methods have brought required distribution in each age class. It is suggested, depending on the character of material being transformed, to use all reviewed methods in order to achieve proper distribution in each age class.

Adolescent↗

PubMed1998

A trivariate distribution for the height, weight, and fat of adult men.

Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the U.S. Veterans Administration's "Normative Aging Study" in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4-year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models.

Adipose Tissue↗

PubMed2002

An adaptive test of significance for a subset of regression coefficients.

An F-test for a subset of regression coefficients is often used in order to compare two nested linear models. An adaptive test is proposed that has higher power than this F-test for many non-normal distributions of error terms. The adaptive test uses a weighted least squares procedure with weights determined from the Studentized deleted residuals from a linear model. A permutation method is then used so that the resulting test maintains its size near the nominal value. Results from several simulation studies are used to compare the power of the adaptive test to the F-test. The adaptive test is recommended as a way of increasing the power of many common tests when used with models that have few parameters whenever the distribution of errors is non-normal and the number of observations exceeds 20.

Computer Simulation↗

PubMed1980

Serum complement levels in patients with cancer of the uterine cervix before and after radiation therapy.

With single radial immunodiffusion method the level of the third component of the complement was investigated in 153 cervix cancer patients. In some cases the level of the fourth component of the complement and total hemolytic activity of the complement were parallely determined. The C'3 values elicited a polarized distribution pattern in contrast to the normal distribution of the controls. Mean C'3 level increased simultaneously with the progress of the disease up to Stage III, and decreased only in Stage IV. On the contrary, C'4 level was stable and practically equaled the normal value. Total hemolytic activity of the complement in cervix cancer patients usually exceed normal values. The C'3 changes during radiation therapy contradicted its role as an acute phase protein.

Adult↗

PubMed1991

A criterion for a standardized definition of low birthweight.

A criterion for the definition of low birthweight (LBW) which is tailored to each population group is presented. The suggested criterion is based on an assumption according to which the distribution of birthweight is actually a mixture of the following two components: the predominant (including about 95% of the newborns and is normally distributed) and the residual (assumed to be mainly composed of newborns under extreme risk for perinatal mortality). The LBW category is defined to include a small but equal (for all groups) percentage of the predominant component. Thus, population groups which differ with respect to their specific predominant birthweight distribution are comparable with respect to the perinatal mortality risk. Application of the suggested definition is demonstrated using data from two ethnic groups in Israel. Results show a smaller percentage of female LBW than males in both population groups when using the suggested criterion. The reverse is observed (i.e. more male than female LBW), using the standard criterion (less than 2500 gm). The suggested criterion is shown to reduce the sex and ethnic differences in perinatal mortality among the respective LBW categories.

Asia↗

PubMed2004

Role of myosin VIIa and Rab27a in the motility and localization of RPE melanosomes.

Myosin VIIa functions in the outer retina, and loss of this function causes human blindness in Usher syndrome type 1B (USH1B). In mice with mutant Myo7a, melanosomes in the retinal pigmented epithelium (RPE) are distributed abnormally. In this investigation we detected many proteins in RPE cells that could potentially participate in melanosome transport, but of those tested, only myosin VIIa and Rab27a were found to be required for normal distribution. Two other expressed proteins, melanophilin and myosin Va, both of which are required for normal melanosome distribution in melanocytes, were not required in RPE, despite the association of myosin Va with the RPE melanosome fraction. Both myosin VIIa and myosin Va were immunodetected broadly in sections of the RPE, overlapping with a region of apical filamentous actin. Some 70-80% of the myosin VIIa in RPE cells was detected on melanosome membranes by both subcellular fractionation of RPE cells and quantitative immunoelectron microscopy, consistent with a role for myosin VIIa in melanosome motility. Time-lapse microscopy of melanosomes in primary cultures of mouse RPE cells demonstrated that the melanosomes move in a saltatory manner, interrupting slow movements with short bursts of rapid movement (>1 RR01183m/second). In RPE cells from Myo7a-null mice, both the slow and rapid movements still occurred, except that more melanosomes underwent rapid movements, and each movement extended approximately five times longer (and further). Hence, our studies demonstrate the presence of many potential effectors of melanosome motility and localization in the RPE, with a specific requirement for Rab27a and myosin VIIa, which function by transporting and constraining melanosomes within a region of filamentous actin. The presence of two distinct melanosome velocities in both control and Myo7a-null RPE cells suggests the involvement of at least two motors other than myosin VIIa in melanosome motility, most probably, a microtubule motor and myosin Va.

Animals↗

PubMed1996

A comparison of different approaches for fitting centile curves to birthweight data.

Centile charts, plotted by week of gestational age, are widely used clinically to decide whether a child is 'small-for-dates', indicating that there may have been some cause of intra-uterine growth retardation. A variety of different statistical techniques have been proposed for constructing centile charts. Some methods are distribution free and work on the basis of obtaining and then smoothing the empirical centiles. In others the centiles are calculated assuming a Normal distribution either of the raw data or of transformed data. In Scotland the details of each maternity admission are entered onto an SMR2 form and these records are stored centrally by the Scottish Health Service. A data set consisting of all live births occurring in Scottish hospitals between 1980 and 1992 is used to compare different approaches to constructing centile charts.

Birth Weight↗

PubMed2001

Analysis of aerosol distribution inside the object "shelter" at the Chernobyl nuclear reactor site.

Results of the aerosol sampling inside the Object Shelter at the Chornobyl nuclear reactor site are considered in the work. The results show a consistent and significant contribution of submicron fraction to the total aerosol activity. Different methods of interpretation of impactor data series are compared in order to indicate and detect in the most effective way the submicron fraction as a separate component of the distribution. The methods used are as follows-method of probabilistic-logarithmic scale, method of likelihood function, non-linear approximation by sum of several log-normal distributions, and restoration of the initial distribution using passage functions of impactor cascades. Practically all the collected data on aerosol distribution inside the Shelter show a distinct submicron component. The contribution of the submicron component into the total aerosol activity is about 35%. Influence of the actual aerosol distribution on the dose coefficients is analyzed.

Aerosols↗

PubMed1989

Sample size tables for logistic regression.

Sample size tables are presented for epidemiologic studies which extend the use of Whittemore's formula. The tables are easy to use for both simple and multiple logistic regressions. Monte Carlo simulations are performed which show three important results. Firstly, the sample size tables are suitable for studies with either high or low event proportions. Secondly, although the tables can be inaccurate for risk factors having double exponential distributions, they are reasonably adequate for normal distributions and exponential distributions. Finally, the power of a study varies both with the number of events and the number of individuals at risk.

Adult↗

PubMed2001

Adsorption-Energy Distribution of Heterogeneous Surfaces Predicted by Projections onto Convex Sets.

The method of projections onto convex sets (POCS) is used to calculate the adsorption-energy distribution function from the adsorption integral (using a modified Langmuir local isotherm) for energetically heterogeneous surfaces. The POCS method, originally developed in the 1960s, has been successfully applied for many years to estimation problems, mainly in the fields of image processing, signal recovery, and optics. It allows one to incorporate into an iteration scheme available information about the experimental data and the measurement error as well as a priori constraints (such as nonnegativity) based on physical reasoning. It is important to note that the POCS method does not lead to a unique "optimum" solution. Rather, a feasible solution that is consistent with all imposed contraints is found within a "solution space". The "size" of this solution space depends on how large the measurement errors are; it also depends on the accuracy of the error statistics and the number and significance of a priori constraints used. In several examples, the POCS method is used to recover energy distributions from simulated adsorption data containing normally distributed errors. The excellent recoveries obtained demonstrate the value of the POCS method as a robust and reliable tool for adsorption-integral inversions. Copyright 2001 Academic Press.

Journal Article↗

PubMed1985

Proliferation of thalamic afferents in cerebral cortex altered by callosal deafferentation.

In area 41, the auditory region of rat neocortex, callosal afferents project to layers I through III and thalamic afferents project to deep layer III through IV. Thus, these two extrinsic systems of afferents project simultaneously to only a narrow lamina in mid to low layer III. For this study, this narrow region of overlap is quantitatively examined to determine the distribution of callosal and thalamic afferents by observing degenerating terminals produced by separate callosal and thalamic lesions. The results show that of all asymmetric synapses observed in the neuropil of this narrow zone, 84% are dendritic spines and the balance are dendritic shafts. Although both callosal and thalamic afferents prefer to synapse with dendritic spines in the neuropil, 78% of the thalamic afferents synapse with dendritic spines while 93% of the callosal afferents synapse with dendritic spines. Vaughan & Foundas (1982) have shown that 3 months after callosal lesions in 1-month-old animals, additional thalamic axons have grown into, and proliferated in, this part of mid to low layer III. Quantitative analysis of the distribution of the degenerating thalamic axon terminals in these long-term callosally lesioned animals has been used to determine whether the proliferating thalamic afferents demonstrate any specificity in the pattern of synapses they make or whether the callosally deafferented neurons determine the pattern of synapses. The results indicate that thalamic axons do exhibit axon specificity, for after they have proliferated into the callosal domain, 80% of the degenerating terminals synapse with dendritic spines and 20% synapse with shafts. This distribution is most comparable to the normal distribution of thalamic axons in this region.

Animals↗

PubMed1975

[Quantitation of basophil cell-line in human bone marrow (author's transl)].

Appropriately fixed basophil cell-line can selectively be visualized by anionic dyes as toluidine blue. Typical activities for Leder's esterase distinguish individual maturity stages. Both methods were successively applied to bone marrow smears from 22 healthy subjects in order to assess the basophil population among the total marrow leukocytes (lymphocytes, monocytes and granulopoietic cell-lines) and the portion of each basophil maturity stages. Total basophils represent 0.45+/-0.13% of marrow leukocytes. Basophil precursors capable of division (promyelocytes and myelocytes) comprise 46.7%, mitoses 3.7+/-1.76% of the total marrow basophil population. The frequency distribution of these subpopulations approximated a normal distribution pattern. No clear central tendencies could be encountered in the dispersion of other stages. The low peripheral basophil counts, the high incidence of divisible precursors and the considerable mitotic activity suggest a short half-life time for blood basophils.

Basophils↗

PubMed1985

Statistical comparison of Pearl rates.

Statistical procedures for hypothesis testing and interval estimation of the difference in a pair of Pearl rates are presented. The p value of the test statistic is evaluated exactly from the binomial distribution or approximately from the standard normal distribution. Interval estimation is provided by the test-based method of Miettinen. The procedures are applied to two published data sets, and the conceptual link between the Pearl rate and life-table methods is discussed.

Actuarial Analysis↗

PubMed1994

Study of the apices of human permanent teeth with the use of a scanning electron microscope.

The apical region of the roots of 38 maxillary incisors, 25 mandibular incisors, 29 maxillary second premolars, 92 mandibular first and second premolars, 12 maxillary first molars, and 17 mandibular first molars were prepared and studied with the use of a scanning electron microscope. The number and size of the main apical foramina, their distance from the anatomic apex, and the existence and size of accessory foramina were recorded, summarized, and statistically analyzed. More than one main foramen was observed in all groups except for the palatal root of maxillary molars and the distal root of mandibular molars. Accessory foramina were also observed in all groups of teeth. The distal roots of mandibular molars had the largest size main foramen (mean value, 392 microns), whereas the maxillary premolars had the largest accessory foramina (mean value, 53.4 microns) and the most complicated apical morphologic makeup. The distance of the main foramen from the anatomic apex never exceeded 1 mm. The highest values were observed at the mandibular incisors (978 microns), the distal root of mandibular molars (818 microns), and the upper premolars (816 microns). All values showed satisfactory fitting to normal distribution.

Chi-Square Distribution↗

PubMed1981

Distribution of IgE in a community population sample: correlations with age, sex, and allergen skin test reactivity.

The distribution of total serum IgE determined by the paper radioimmunosorbent test (PRIST) is examined in a large random stratified community population. Prior to logarithmic conversion the distribution of this immunoglobulin is not normal, with almost 40% of values below 20 IU/ml. A normal distribution occurs following such conversion, with a geometric mean value of 32.1 IU/ml. Both age and sex, in addition to atopic status, relate to IgE level. In both sexes highest levels occur among 6- to 14-year-olds, and males have higher levels than females at any given age. Women over age 75 yr have the lowest levels (geometric mean 9.2 IU/ml). Subjects with positive skin test results have several times the concentration of IgE as their nonatopic counterparts.

Adolescent↗

PubMed2006

Quantitative sensory testing: a comprehensive protocol for clinical trials.

We have compiled a comprehensive QST protocol as part of the German Research Network on Neuropathic Pain (DFNS) using well established tests for nearly all aspects of somatosensation. This protocol encompasses thermal as well as mechanical testing procedures. Our rationale was to test for patterns of sensory loss (small and large nerve fiber functions) or gain (hyperalgesia, allodynia, hyperpathia), and to assess both cutaneous and deep pain sensitivity. The practicality of the QST protocol was tested in 18 healthy subjects, 21-58 years, half of them female. All subjects were tested bilaterally over face, hand and foot. We determined thermal detection and pain thresholds including a test for the presence of paradoxical heat sensations, mechanical detection thresholds to von Frey filaments and a 64-Hz tuning fork, mechanical pain thresholds to pinprick stimuli and blunt pressure, stimulus-response-functions for pinprick and dynamic mechanical allodynia (pain to light touch), and pain summation (wind-up ratio) using repetitive pinprick stimulation. The full protocol took 27+/-2.3 min per test area. The majority of QST parameters were normally distributed only after logarithmic transformation (secondary normalization) except for the frequency of paradoxical heat sensations, cold and heat pain thresholds, and for vibration detection thresholds. Thresholds were usually lowest over face, followed by hand, and then foot. Only thermal pain thresholds, wind-up ratio and vibration detection thresholds were not significantly dependent on the body region. There was no significant right-to-left difference for any of the QST parameters; left-to-right correlation coefficients ranged between 0.78 and 0.97, thus explaining between 61% and 94% of the variance. This study has shown that a complete somatosensory profile of one affected area and one unaffected control area, which will be necessary to characterize patients with a variety of diseases, can be obtained within 1 h. Case examples of selected patients illustrate the value of z-transformed QST data for an easy survey of individual symptom profiles.

Adult↗

PubMed2005

Analysis of concentration characteristics in ultrasonic atomization by droplet diameter distribution.

The droplet diameter distribution and concentration characteristics in ultrasonic atomization were experimentally studied. The samples were aqueous solutions of methanol, ethanol and 1-propanol. The diameter distribution of atomized droplets showed the normal distribution, and the median diameter and standard deviation were expressed by means of the ultrasonic condition and the liquid properties. The concentration characteristic in ultrasonic atomization was analyzed by using the model of shell and core to the atomized droplet, where the former and latter consist of solute and solution, respectively. The value, which was surface solute amount in droplet multiplied by the molecular volume, increased with increasing solute molar fraction in bulk liquid and was independent of alcohol kinds. The rate of accompanying liquid and the solute molar fraction in accompanied liquid were estimated from the diameter distribution and the surface solute amount in droplet.

Alcohols↗

PubMed1998

Study on urine boron reference values of Japanese men: use of confidence intervals as an indicator of exposure to boron compounds.

A simple and rapid method for the determination of urine boron by inductively-coupled plasma argon emission spectrometry (ICPAES) has been developed to establish boron exposure guidelines. After 11-fold dilution in 18.25 M omega cm ultra-pure water and vigorous shaking, urine may be directly injected into the spectrometer, providing accurate and reproducible results. We report the results obtained with urine samples obtained from a group of male Japanese electronic workers (n = 102) who had not been exposed to boron; boron concentrations were corrected with use of a specific gravity of 1.024 g/ml. The frequency distribution resulted in a log-normal distribution diagram for anatomical spread. The geometric mean values for urine boron in the non-exposed workers was 798.0 micrograms/l, while the confidence interval (C.I.) was between 398.1 and 1599.6 micrograms/l. Taking into consideration the short biological half-life of boron and its major excretion route via urine, urine was considered to be a suitable means for monitoring of exposure to this element. We conclude that the guidelines established by determining boron reference values are useful for the protection of individuals exposed to boron in their working environments.

Adult↗