Constancy Of Ratio Research Articles

Brazilian Companies’ Dividend Payout in a Political Uncertainty Scenario

The analysis of the determinants of the dividend payout policy becomes even more relevant in a context of crisis. In this scenario, companies wonder which strategy shall prevail—either to keep the payout ratio constancy to signal to the market positive aspects about themselves or to adapt it to the external conjuncture, protecting themselves from future uncertainties. This being so, this study aims at identifying the determinants of the dividend payout policy, in the period before and after the former President Dilma Rousseff’s impeachment, by using logarithmic and probabilistic regression models. To this end, a sample of Brazilian non-financial publicly-held companies is considered, whose data are obtained from the Capital IQ base. As a result, the corporate dividend policy is identified as not being affected by the market environment. Such a fact indicates that Brazilian companies choose to maintain their dividend payout policy, even in scenarios of political uncertainty. This study differs from the others for analyzing the relationship between dividend payout decisions, whether in times of stability or in political and economic crisis.

Estimated lower speed boundary at which the walk ratio constancy is broken in healthy adults.

[Purpose] The ratio of step length to cadence (walk ratio) is invariant over a wide range of speeds. However, no studies have investigated details of the change in the walk ratio at slow speeds. It is necessary to explore how walking behavior changes at a low speed to understand the slow walking observed in various conditions such as aging and pathological conditions. In this study, changes in the walk ratio at slow speeds were investigated, and a lower boundary was estimated at which the walk ratio constancy is broken. [Subjects and Methods] Twenty-one healthy adults were instructed to walk along a flat, straight walkway at five different speeds (fast, preferred, slightly slow, slow, and very slow). The walk ratio was calculated from the step length and cadence. [Results] As the walking speed decreased, the walk ratio and variance began to increase abruptly. The initial break in the walk ratio constancy was at approximately 62 m/min. In addition, the boundary of cadence was approximately 98 m/steps/min. [Conclusions] The study successfully determined a lower boundary at which the walk ratio constancy was broken, suggesting that different control strategies are used when walking at less than the gait speed at which constancy is broken in healthy adults. The finding provides valuable information for understanding slow walking observed in individuals with various pathological conditions.

Ti/Zr ratio as a geochemical tool for the correlation of weathered coals from geological formations in two Latin American sedimentary basins

ABSTRACTMajor and trace element concentrations in fresh and altered coals in outcrops and coalfields from Táchira and Mérida states (Venezuela), as well as from Napo and Pastaza provinces (Ecuador), have been determined to establish inorganic parameters not dependent of weathering effects. Noteworthy is that the Ti/Zr ratio is approximately constant in each sedimentary basin even for great distances (>100 km). Worldwide data of trace elements analysis in coal samples support the stated Ti/Zr ratio constancy in different basins for fresh and weathered ones. Therefore, Ti/Zr ratio can be considered a rapid tool to easily identify coal seam correlations.

Recovering of weather degraded images based on RGB response ratio constancy.

Images captured under bad weather conditions suffer from poor contrast and visibility. These effects are noticeable for haze, mist, fog, or dust storms. We have proposed a recovering method for images captured for several adverse weather conditions based on the RGB response ratio constancy under illuminant changes. This algorithm improves the visibility, contrast, and color in degraded images with low computational times. We obtain results similar to those from previously published deweathering methods but with no prior information about the image content or atmospheric parameters needed.

Geochemical features of Uranium isotopes in waters of the Toktogulsky reservoir

Proportions of water mix of different genesis influencing feeding ofrivers of the Toktogulsky reservoir were calculated basing on the results of study of uranium content and ratio of its even isotopes. Constancy of ratio of uranium isotopes in the waters of the Toktogulsky reservoir was shown, which can be used as a natural indicator during assessment of pollution of waters of the Naryn River basin by lower uranium tailing dumps.

Color changes in objects in natural scenes as a function of observation distance and weather conditions

We have analyzed the changes in the color of objects in natural scenes due to atmospheric scattering according to changes in the distance of observation. Hook-shaped curves were found in the chromaticity diagram when the object moved from zero distance to long distances, where the object chromaticity coordinates approached the color coordinates of the horizon. This trend is the result of the combined effect of attenuation in the direct light arriving to the observer from the object and the airlight added during its trajectory. Atmospheric scattering leads to a fall in the object's visibility, which is measurable as a difference in color between the object and the background (taken here to be the horizon). Focusing on color difference instead of luminance difference could produce different visibility values depending on the color tolerance used. We assessed the cone-excitation ratio constancy for several objects at different distances. Affine relationships were obtained when an object's cone excitations were represented both at zero distance and increasing distances. These results could help to explain color constancy in natural scenes for objects at different distances, a phenomenon that has been pointed out by different authors.

Relational color constancy in the absence of ratio constancy: 3D scenes with spatially inhomogeneous illumination

Relational color constancy in the absence of ratio constancy: 3D scenes with spatially inhomogeneous illumination

Scaling relative incentive value: Different adjustments to incentive downshift in pigeons and rats

Previous research suggests that pigeons and rats show differences in their behavioral adjustments in spaced-trial, incentive-downshift situations. Also, Papini and Pellegrini [Papini, M.R., Pellegrini, S., 2006. Scaling relative incentive value in consummatory behavior. Learn. Motiv. 37, 357-378] and Pellegrini and Papini [Pellegrini, S., Papini, M.R., 2007. Scaling relative incentive value in anticipatory behavior. Learn. Motiv. 38, 128-154] showed that changes in the rat's lever-pressing performance, runway running, and consumption of sucrose solutions after downshifts in incentive magnitude were a function of the ratio of postshift/preshift incentive magnitudes. Here, two experiments using a Pavlovian autoshaping procedure studied the adjustment of pigeons and rats to changes in incentive magnitude. In Experiment 1, pigeons received light-food pairings, whereas in Experiment 2, rats received lever-sucrose pairings. As a result, key-pecking and lever-pressing developed in each experiment, respectively. Preshift incentive magnitudes were downshifted so as to obtain postshift/preshift ratios of 0.125 and 0.25. Pigeons responded during the postshift phase according to the preshift incentive value and independently of the ratio value. However, rats showed ratio constancy, responding during the postshift in accordance with the postshift/preshift ratio, rather than with the absolute magnitudes of either the preshift or postshift incentives. These results support the comparative hypothesis that the mechanisms underlying ratio constancy during incentive downshifts are unique to mammals.

Overdispersion of body size in Australian desert lizard communities at local scales only: no evidence for the Narcissus effect

Both local and regional processes may contribute to community diversity and structure at local scales. Although many studies have investigated patterns of local or regional community structure, few have addressed the extent to which local community structure influences patterns within regional species pools. Here we investigate the role of body size in community assembly at local and regional scales in Ctenotus lizards from arid Australia. Ctenotus has long been noted for its exceptional species diversity in the Australian arid-zone, and previous studies have attempted to elucidate the processes underlying species coexistence within communities of these lizards. However, no consensus has emerged on the role of interspecific competition in the assembly and maintenance of Ctenotus communities. We studied Ctenotus communities at several hundred sites in the arid interior of Australia to test the hypothesis that body sizes within local and regional Ctenotus assemblages should be overdispersed relative to null models of community assembly, and we explored the relationship between body size dispersion at local and regional scales. Results indicate a striking pattern of community-wide overdispersion of body size at local scales, as measured by the variance in size ratios among co-occurring species. However, we find no evidence for body size overdispersion within regional species pools, suggesting a lack of correspondence between processes influencing the distribution of species phenotypes at local and regional scales. We suggest that size ratio constancy in Ctenotus communities may have resulted from contemporary ecological interactions among species or ecological character displacement, and we discuss alternative explanations for the observed patterns.

Assembly rules for New England ant assemblages

Community assembly rules specify patterns of species co‐occurrence and morphology dictated by interspecific competition. We collected data on the occurrence of ground‐foraging ant species in 22 ombrotrophic bogs and adjacent forest plots of New England to test two general assembly rules: reduced co‐occurrence of species among communities, and even spacing of body sizes of species within communities. We used null models to generate random communities unstructured by competition and evaluated patterns at regional and local spatial scales. At the regional scale, species co‐occurrence in forests, but not bogs, was less than expected by chance, whereas, at the local scale, co‐occurrence in both habitats was not different from random. At the regional scale, spacing of body size distributions was random (in bogs) or aggregated (in forests). At the local scale, body size patterns were weakly segregated in bogs, but random or weakly aggregated in forests. In bogs, size ratio constancy was accompanied by greater generic diversity than expected. Although assembly rules were originally developed for vertebrate communities, they successfully explained some patterns in New England ant assemblages. However, the patterns were contingent on spatial scale, and were distinctly different for bog and forest communities, despite their close proximity and the presence of many shared species in both assemblages. The harsh physical conditions of bogs may act as a habitat filter that alters community assembly rules.

Differential Mobility of Elements in Burial Diagenesis of Siliciclastic Rocks

ABSTRACT Mass-balance calculations involving smectite-rich siliciclastic mudstones sampled from boreholes show that significant K2O addition and CaO loss correlate strongly with the progress of illitization of smectite and with the dissolution of calcite. The calculations are based on the immobility of Al2O3, and require a chemically homogeneous sediment at deposition, such that the shallower samples represent protolith compositions of deeper samples. Constancy of ratios of TiO2/Al2O3 are used to (1) establish that both TiO2 and Al2O3 have similarly low differential mobilities, and (2) identify stratigraphic sections available in the literature that are sufficiently homogeneous to allow the calcu ations. Our calculations show that most major-oxide components are immobile at the 5% limit of resolution of the calculations. Exceptions are K2O, which is almost universally added to mudstones, and CaO, which is commonly removed from mudstones during diagenesis. The addition of up to 50% K2O correlates with percent illite in mixed-layer illite/smectite, indicating that illitization of smectite involves fixation of K2O from diagenetic fluids. Removal of 40% CaO from some sections correlates with decreasing calcite mode and is attributed to dissolution of calcite. Together these reactions lead to a 10-15% loss of mineral volume, a volume loss that must be added to porosity loss when modeling compaction. Illitization and carbonate dissolution may be linked, because K-fixation during illitization decreases the pH of the local fluid (a reverse weathering reaction), which enhances carbonate dissolution. Addition of up to 20% Na2O in some rocks may be caused by albitization of plagioclase, but Na2O addition is not pervasive. The apparent lack of mass transfer associated with dissolution of kaolinite and feldspars or precipitation of chlorite implies that these reactions are balanced by other reactions such that their oxide components in mudstones are conserved. Limited data from sandstone-mudstone pairs are consistent with transfer of K2O from sandstones to mudstone via rising diagenetic fluids. Except for CaO and the alkalis, diagenesis of siliciclastic mudstones appears isochemical (± 5% relative) for most major oxide components. The much larger changes recorded in some reservoir sandstones are clearly exceptions, and may not reflect changes occurring at the scale of kilometers.

Trace element behavior in the alkali basalt-comenditic trachyte series from Mururoa Atoll, French Polynesia

Numerous drill holes have penetrated close to 1000 m of the volcanic pile of Mururoa atoll. The rocks are a typical example of mildly alkaline intraplate basaltic volcanics ranging from Mg-rich compositions to comenditic trachytes. Evolved basalts and hawaiites are the dominant rock types. Benmoreites and trachytes are relatively uncommon. The available KAr ages indicate a long period of activity between 11.8 and 10.7 Ma. Nevertheless, all the volcanic rocks studied are cogenetic in a broad sense (identical 143 Nd 144 Nd and initial 87 Sr 86 Sr ratios, constancy of ratios of highly incompatible elements). No indications of the occurrence of assimilation or magma mixing have been found. The Mururoa series is thus suitable for the study of fractionation-related processes. Three crystallization/fractionation models have been tested using trace elements, the mineral proportions taken from mass-balance calculations on major elements and individual distribution coefficients determined from trace element data on phenocrysts/host rock pairs. Closed-system fractional crystallization (CSF) is consistent with all of the trace element data. It satisfactorily reproduces the trends observed for compatible and incompatible elements, including the complex behavior of Y and rare-earth elements which are fractionated by kaersutite and apatite in mugearitic and benmoreitic magmas. In situ crystallization and equilibrium crystallization produce trends very close to Rayleigh's law model for most incompatible elements. In contrast, in situ and equilibrium crystallization models produce significant underdepletions (compared to CSF) in compatible elements (Sc, Cr, Co, Ni). The corresponding patterns are not consistent with our analytical data in intermediate and evolved rocks. Cooling calculations indicate, however, that the length of volcanic activity in Mururoa ( ≥ 1 Ma) is hardly compatible with closed-system fractional crystallization of a single magma batch. Various models of open-system fractionation have thus been tested, but generally they do not fit the observed trace element patterns. However, one peculiar case of open-system fractionation in a periodically replenished magma chamber is consistent with the data. In this model, batches of mantle-derived parent liquids filling up the chamber at the beginning of each cycle evolve by fractional crystallization. All the corresponding residual liquids either crystallize or erupt at the end of each cycle, before the next replenishment. Thus, the apparently cogenetic Mururoa series is likely to result from fractional crystallization occurring under similar conditions through time, either in several magma chambers or in a single periodically refilled reservoir.

HUTCHINSONIAN RATIOS AND LOG-NORMAL DISTRIBUTIONS.

It has been proposed that competition among members of a species assemblage leads to constant size ratios among the species ranked in order of average individual size, or to large minimum size ratios (for references, see Simberloff and Boecklen, 1981). Simberloff and Boecklen (1981) present statistical tests for constancy of size ratios and for large minimum size ratios in species assemblages (sensu Hutchinson, 1959) and apply these tests to appropriate data from the literature. The tests for ratio constancy are based on those developed by Barton and David (1956) to determine whether points along a line are unlikely to be the result of independent uniform-random placement. The test for minimum size ratios is based on Irwin's (1955) probability distribution function for the minimum segment produced by independent uniform-random placement of points along a unit line. To determine whether sets of species manifest constant size ratios or large minimum ratios, Simberloff and Boecklen use these tests to determine whether species are constantly spaced or exhibit large minimum distances along a log-scaled line. Asking whether the logarithms of sizes are constantly spaced or have a large minimum distance along a line is equivalent to asking whether size ratios are constant or exhibit large minima along an arithmetic line since log(a/ b) = log a log b, log(b/c) = log b log c, etc. Simberloff and Boecklen find, in a compilation of species assemblages adduced to demonstrate the existence of constant ratios and large minimum ratios, only seven of 21 claims of ratio constancy and seven of 18 claims of large minima supported at the 5% level, and only about half the claims supported at the 30% level. Schoener (1984), Colwell and Winkler (1984), and Case et al. (1983) challenge these results, claiming that the tests used by Simberloff and Boecklen assume a biologically unrealistic uniform distribution of sizes. Colwell and Winkler suggest that a modal distribution is more appropriate; Schoener and Case et al. recommend a log-normal distribution. Furthermore, they claim that the assumption of a uniform distribution biases the tests toward failing to reject the null hypothesis. The tests used by Simberloff and Boecklen assume a log-uniform distribution of sizes-not a uniform distribution. Nevertheless, a log-normal distribution of sizes may be more realistic and the performance of the BartonDavid and Irwin test statistics, as used by Simberloff and Boecklen, should be investigated under this assumption, Critics of null models contend that particular assumptions of null models may invalidate them as appropriate reference points for evaluating evolutionary processes that are assumed to structure communities and species interactions (Hendrickson, 1981; Diamond and Gilpin, 1982) or that historical effects (Colwell and Winkler, 1984) or multiple causality (Quinn and Dunham, 1983) may insulate community theory from direct refutation by null models. Criticisms of the assumptions of null models have the advantage that they may be addressed in a rigorous and quantitative manner. Here we present a sensitivity analysis that assesses the performance of the Barton-David and Irwin test statistics when data are drawn from a log-normal distribution. We compare the cumulative distributions of the test statistics generated from the log-normal distribution to those generated by the Barton-David and Irwin probability distribution functions. The cumulative distributions for each test statistic are based upon the average of five sets of 5,000 replicates for species assemblages of five, six, and ten. Averaging the five sets of 5,000 replicates produces precise estimates with minimal sampling variation.

Sex Ratio Constancy in the Red-Winged Blackbird

Sex Ratio Constancy in the Red-Winged Blackbird

Partial degrees of substitution in cellulose nitrates determined by means of 13C magnetic resonance studies

High resolution 13C n.m.r. proton noise decoupled (75.5 MHz) spectra have been recorded for a series of nitrated celluloses and denitrated cellulose nitrates. From the detailed spectral assignments an analysis of the partial degrees of substitution and distribution of nitrate groups in the β-D-glucopyranose residues is presented. The data are compared with the predictions of a model based on the constancy of ratio of three equilibrium constants for nitration—denitration at the C2, C3 and C6 positions for differently substituted β-D-glucopyranose residues and it is shown that the situation is considerably more complex than provided for by the model. Analysis of the anomeric 13C carbon region produces some sequence information which indicates non-random distribution of nitrate ester groups.

On the chemical composition of atmospheric aerosols — Part I: Some stoichiometric aspects of the problem

Following a recent hypothesis on the role of activated sodium chloride particles as possible condensation and sublimation nuclei, an analysis of data given byC. Junge on the chemical composition of aerosols, is made. It is established that all reported giant nuclei fall into three distinct categories of composition and that within each of these categories the ratio of the sums of anions to the sums of cations for constituents for which analyses were made, remains remarkably constant throughout the days of sampling, and for both geographic positions at which sampling has been carried out. A dependence of the hydroxide-carbonate content, on that of nitrate is also indicated in the «alkaline» nuclei. The system is treated as a saturated solution, and it is shown by the procedure of continuous variations that singularities occur at particular ratios of the prevalent chemical groups in solution, possibly indicating formation of complex species. This, together with the presence of double salts in the solid phase may be partly the reason for the constancy of ratio of sums in the groups of particles studied byJunge, while the grouping itself may depend on the origin and subsequent transformations of the particles.

Lipides of chick heart fibroblasts; effect of vitamin B12 and folic acid.

Summary1. A study of amount and nature of lipides that accumulate in “old” cultures of chick heart fibroblasts was made, along with the effect of vit. B12 and folic acid on the accumulation. 2. Vit. B12 and folic acid in the medium prevented accumulation of fat and apparently stimulated growth of the culture. Normal controls, freshly excised tissue, and vitamin treated cultures were essentially free of neutral fat as indicated by constancy of ratio of fatty acids to phospholipide phosphorus. In degenerating cultures this ratio increased rapidly in the absence of added vitamins.

An Improved Radiation Pyrometer

In designing a new radiation pyrometer for industrial use above the lower limit of visible radiation, consideration of ambient temperature effects, which is of much importance in modern industrial practice, was carried out by aid of mathematical analysis. In one hypothetical case, with a very sensitive type of thermopile losing heat from its hot junction by radiation alone, it is shown that an increase in operating ambient temperature of 180°F (from 80°F to 260°F) results in a drop in output voltage of 38 percent for a constant furnace temperature of 1300°F. The corresponding error in reading is 315°F. At a furnace temperature of 3000°F, the decrease in voltage is 17 percent and the error in reading is 387°F. Under similar conditions, in another hypothetical case of a less sensitive thermopile constructed to lose much of its heat by thermal conduction, this 180°F increase in operating ambient temperature would result in a decrease in output voltage of from 12.2 percent to 12.5 percent for any furnace temperature between the two values mentioned. The error in reading would range from 58°F to 162°F over the stated span of furnace temperatures. The constancy of ratio of e.m.f.'s shown for the higher conduction factor makes it possible to provide ambient temperature compensation over a wide range of furnace temperatures with a nickel shunt compensator. The pyrometer here described, designed along these lines, shows ambient temperature errors of less than three degrees F in the furnace temperature being measured for ambient temperature variations from 50° to 200°F; transient errors would usually be one degree or less for most cases; the response is complete within 3.5°F in four seconds and within half a degree or less in six seconds. The calibration, with varying ratios of distance-to-target versus target diameter up to over 20 to 1, is unusually constant. A thermopile of ten units insures ample e.m.f. All of the thermopile junctions are spot-welded and the construction is arranged throughout to withstand high ambient temperatures.