Idiosyncratic volatility around information release date

Several papers document idiosyncratic volatility is time-varying and many attempts have been made to reveal whether idiosyncratic risk is priced. This research studies behavior of idiosyncratic volatility around information release dates and also its relation with return after public announcement. The results indicate that when a company discloses specific information to the market, firm’s specific volatility level shifts and short-horizon event-induced volatility vary significantly however, the category to which the announcement belongs is not important in magnitude of change. This event-induced volatility is not small in size and should not be downplayed in event studies. Moreover, this study shows stocks with higher contemporaneous realized idiosyncratic volatility earn lower return after public announcement consistent with “divergence of opinion hypothesis”. While no significant relation is found between EGARCH estimated idiosyncratic volatility and return and also between one-month lagged idiosyncratic volatility and return presumably due to significant jump around public announcement both may provide some signals regarding future idiosyncratic volatility through their correlations with contemporaneous realized idiosyncratic volatility. Finally, the study show that positive relation between return and idiosyncratic volatility based on under-diversification is inadequate to explain all different scenarios and this negative relation after public announcement may provide a useful trading rule.

Relation between the level of self-mutilation and theconcentration of fecal metabolites of glucocorticoids incaptive chimpanzees (Pan troglodytes)

The influence of stress in an environment, according with the behavioral and endocrine variables of primates, are increasingly being studied by a diversity of authors, and have shown that abnormal behaviors associated with increased glucocorticoids may be directly related with the impairment of their well-being. In this work were used 22 adult chimpanzees (Pan troglodytes), 11 males and 11 females, kept in captivity in three different institutions. All animals had their behavior registered by focal session using a 30 seconds sample interval, during six months, totaling 4,800 registries per each animal. During this period, fecal samples were collected 3 times a week for the extraction and measurement of the concentration of fecal metabolites of glucocorticoid by radioimmunoassay. Of the total observed, stereotypical behaviors represented 13,45±2.76%, and among them, self-mutilation represented 38.28±3.98 %. The animals were classified into three different scores, according with the percentage of body surface with alopecia due to self-mutilation. It was found a positive correlation of high intensity between the scores of alopecia due to the observed mutilation and the average concentrations of fecal metabolites of glucocorticoids. This result strongly suggests that this measurement of self-mutilation in a chimpanzee can be used as an important auxiliary tool to evaluate de conditions of adaptation of an animal in captivity, functioning as a direct indicator of the presence of chronic stress.

Dental Health in Preschool and Schoolchildren in Relation to Dental Fear and Some Fear-Related Factors, and the Outcome of a Caries Prevention Program in Offspring of Fearful Mothers

Dental caries and dental fear and anxiety (DFA) are common interrelated problems but so far little is known about these problems in Estonia. The aim was to study dental health in relation to DFA, some fear-related factors, and to study the effect of a caries prevention program in children of fearful mothers. Dental health and DFA were assessed in two Estonian [2-4-year-olds (n=472) and 8-10-year-olds (n=344)], and the effect of some medical conditions on DFA in one Finnish child group [3-year-olds (n=148)]. 120 mother-child-pairs participated in the xylitol-based prevention program. Dental health was examined using the WHO or the ICDAS criteria and expressed as dmft/DMFT-indices. The modified children’s fear survey schedule dental subscale (MCFSS-DS) was used to assess DFA of schoolchildren, one single question to assess parental DFA, and the Corah’s dental anxiety scale (DAS) to assess DFA of mothers in the prevention study. Dentine caries was diagnosed in 42% of the 2-4-year-old and in 93% of the 8-10-year-old Estonian children. DFA of 8-10-year-olds (17%) was associated with experience of dental treatment, and maternal and paternal DFA. Dental apprehension at 9 years of age was associated with frequent exposure to invasive medical care. The xylitol-based prevention was successful irrespective of poor dental hygiene habits and maternal severe DFA. In conclusion, experience of operative dental treatment and DFA of Estonian children were closely associated. Invasive medical care and parental DFA were also linked to children’s DFA. Habitual use of xylitol by mothers was effective in preventing caries even in children of severely fearful mothers.

Spontaneous Focusing on Quantitative Relations and the Development of Rational Number Conceptual Knowledge

The aim of the present set of studies was to explore primary school children’s Spontaneous Focusing On quantitative Relations (SFOR) and its role in the development of rational number conceptual knowledge. The specific goals were to determine if it was possible to identify a spontaneous quantitative focusing tendency that indexes children’s tendency to recognize and utilize quantitative relations in non-explicitly mathematical situations and to determine if this tendency has an impact on the development of rational number conceptual knowledge in late primary school. To this end, we report on six original empirical studies that measure SFOR in children ages five to thirteen years and the development of rational number conceptual knowledge in ten- to thirteen-year-olds. SFOR measures were developed to determine if there are substantial differences in SFOR that are not explained by the ability to use quantitative relations. A measure of children’s conceptual knowledge of the magnitude representations of rational numbers and the density of rational numbers is utilized to capture the process of conceptual change with rational numbers in late primary school students. Finally, SFOR tendency was examined in relation to the development of rational number conceptual knowledge in these students. Study I concerned the first attempts to measure individual differences in children’s spontaneous recognition and use of quantitative relations in 86 Finnish children from the ages of five to seven years. Results revealed that there were substantial inter-individual differences in the spontaneous recognition and use of quantitative relations in these tasks. This was particularly true for the oldest group of participants, who were in grade one (roughly seven years old). However, the study did not control for ability to solve the tasks using quantitative relations, so it was not clear if these differences were due to ability or SFOR. Study II more deeply investigated the nature of the two tasks reported in Study I, through the use of a stimulated-recall procedure examining children’s verbalizations of how they interpreted the tasks. Results reveal that participants were able to verbalize reasoning about their quantitative relational responses, but not their responses based on exact number. Furthermore, participants’ non-mathematical responses revealed a variety of other aspects, beyond quantitative relations and exact number, which participants focused on in completing the tasks. These results suggest that exact number may be more easily perceived than quantitative relations. As well, these tasks were revealed to contain both mathematical and non-mathematical aspects which were interpreted by the participants as relevant. Study III investigated individual differences in SFOR 84 children, ages five to nine, from the US and is the first to report on the connection between SFOR and other mathematical abilities. The cross-sectional data revealed that there were individual differences in SFOR. Importantly, these differences were not entirely explained by the ability to solve the tasks using quantitative relations, suggesting that SFOR is partially independent from the ability to use quantitative relations. In other words, the lack of use of quantitative relations on the SFOR tasks was not solely due to participants being unable to solve the tasks using quantitative relations, but due to a lack of the spontaneous attention to the quantitative relations in the tasks. Furthermore, SFOR tendency was found to be related to arithmetic fluency among these participants. This is the first evidence to suggest that SFOR may be a partially distinct aspect of children’s existing mathematical competences. Study IV presented a follow-up study of the first graders who participated in Studies I and II, examining SFOR tendency as a predictor of their conceptual knowledge of fraction magnitudes in fourth grade. Results revealed that first graders’ SFOR tendency was a unique predictor of fraction conceptual knowledge in fourth grade, even after controlling for general mathematical skills. These results are the first to suggest that SFOR tendency may play a role in the development of rational number conceptual knowledge. Study V presents a longitudinal study of the development of 263 Finnish students’ rational number conceptual knowledge over a one year period. During this time participants completed a measure of conceptual knowledge of the magnitude representations and the density of rational numbers at three time points. First, a Latent Profile Analysis indicated that a four-class model, differentiating between those participants with high magnitude comparison and density knowledge, was the most appropriate. A Latent Transition Analysis reveal that few students display sustained conceptual change with density concepts, though conceptual change with magnitude representations is present in this group. Overall, this study indicated that there were severe deficiencies in conceptual knowledge of rational numbers, especially concepts of density. The longitudinal Study VI presented a synthesis of the previous studies in order to specifically detail the role of SFOR tendency in the development of rational number conceptual knowledge. Thus, the same participants from Study V completed a measure of SFOR, along with the rational number test, including a fourth time point. Results reveal that SFOR tendency was a predictor of rational number conceptual knowledge after two school years, even after taking into consideration prior rational number knowledge (through the use of residualized SFOR scores), arithmetic fluency, and non-verbal intelligence. Furthermore, those participants with higher-than-expected SFOR scores improved significantly more on magnitude representation and density concepts over the four time points. These results indicate that SFOR tendency is a strong predictor of rational number conceptual development in late primary school children. The results of the six studies reveal that within children’s existing mathematical competences there can be identified a spontaneous quantitative focusing tendency named spontaneous focusing on quantitative relations. Furthermore, this tendency is found to play a role in the development of rational number conceptual knowledge in primary school children. Results suggest that conceptual change with the magnitude representations and density of rational numbers is rare among this group of students. However, those children who are more likely to notice and use quantitative relations in situations that are not explicitly mathematical seem to have an advantage in the development of rational number conceptual knowledge. It may be that these students gain quantitative more and qualitatively better self-initiated deliberate practice with quantitative relations in everyday situations due to an increased SFOR tendency. This suggests that it may be important to promote this type of mathematical activity in teaching rational numbers. Furthermore, these results suggest that there may be a series of spontaneous quantitative focusing tendencies that have an impact on mathematical development throughout the learning trajectory.

Optimizing the width of strip weeding in arabica coffee in relation to crop age

The aim of this study was to determine the weed strip control (WSC) required for adequate coffee growth after transplanting. A non-irrigated, field-planted (spaced 3.80 x 0.70 m) crop was used. The experimental design was a randomized block, with four replicates. The treatments were arranged in a 9 x 18 split-plot design to test the WSC of 0, 15, 30, 45, 60, 90, 120, 150, and 190 cm, which involved continuously hand-weeding at each side of the coffee row, and 18 coffee growth measurements. Multiple regression analyses were carried out relating to growth-variables as a function of both WSC and growth-evaluation times. Brachiaria decumbens was the main weed accomplishing 88.5% of the total weed dry mass. The minimum width of the WSC increases as the crop ages after transplanting. Assuming reductions of 2% and 5% in the maximum coffee growth, the recommended WSC was 75 and 52 cm at 4 months after transplanting (MAT), 104 and 85 cm at 6 MAT, 123 and 105 cm at 9 MAT, 134 and 116 cm at 12 MAT, 142 and 124 cm at 15 MAT, and 148 and 131 cm at 18 MAT, respectively. It was concluded that integrated weed management in young coffee crops must focus on the weed control only in a minimum range along coffee rows, which increases with coffee plant age, keeping natural vegetation in the inter-rows.

QUALITY OF PROCESSING TOMATO FRUITS IN COMPETITION WITH Solanum americanum

ABSTRACT Five experiments were conducted to evaluate the hypothesis that Solanum americanum density and time of coexistence affect the quality of processing tomato fruit. The tomato crop was established using either the direct drilling or the transplanting technique. The factors evaluated consisted of weed density (from 0 up to 6 plants m-2) and time of weed interference (early bloom stage, full flowering stage, fruit filling, and harvest time). The effects of competition on tomato fruit quality were analysed using a multiple model. Tomato variables evaluated included industrial fruit types (which depended on ripeness and disease infection) and soluble solids level(obrix). Tomato fruit quality is dependent on the factors tested. Under low densities (< 6 plants m-2) of S. americanum there was a small impact on the quality of the tomato fruits. The percentage of grade A (mature fruit with red color and without pathogen infection) tomato fruits is the variable most affect by the independent variables. The impact of these independent variables on the percentage of grade C (green and/or with more than 15% disease infection) tomato yield was of smaller magnitude and in an inverse trend as the observed for grade A. The level of soluble solids was influenced by the weed interference on only two experiments, but the impact was of small magnitude. The impact of the results on current and future crop management practices is discussed.

Along-scan radiometric gradient in Landsat images: understanding the relation between floristic and remote sensing information in tropical forests

The along-scan radiometric gradient causes severe interpretation problems in Landsat images of tropical forests. It creates a decreasing trend in pixel values with the column number of the image. In practical applications it has been corrected assuming the trend to be linear within structurally similar forests. This has improved the relation between floristic and remote sensing information, but just in some cases. I use 3 Landsat images and 105 floristic inventories to test the assumption of linearity, and to examine how the gradient and linear corrections affect the relation between floristic and Landsat data. Results suggest the gradient to be linear in infrared bands. Also, the relation between floristic and Landsat data could be conditioned by the distribution of the sampling sites and the direction in which images are mosaicked. Additionally, there seems to be a conjunction between the radiometric gradient and a natural east-west vegetation gradient common in Western Amazonia. This conjunction might have enhanced artificially correlations between field and remotely-sensed information in previous studies. Linear corrections may remove such artificial enhancement, but along with true and relevant spectral information about floristic patterns, because they can´t separate the radiometric gradient from a natural one.

Relation of the disaccharidases in the small intestine of the rat to the degree of experimentally induced iron-deficiency anemia

Hypolactasia associated with severe iron-deficiency anemia has been reported in several studies. The objective of the present study was to determine whether hypolactasia is associated with the degree and duration of iron-deficiency anemia. Newly weaned male Wistar rats were divided into a control group receiving a diet supplemented with iron (C) and an experimental group (E) receiving a diet not supplemented with iron (iron-deficiency diet). The animals were studied on the 3rd, 5th, 7th, 14th, 21st, 28th and 35th days of the experiment, when overall and iron nutritional status and disaccharidase activity in the small intestine were determined by the Dahlqvist method. A reduction in weight occurred in the anemic animals starting on the 5th day of the study. Anemia was present in the experimental animals, with a progressive worsening up to the 14th day (hemoglobin: C = 13.27 and E = 5.37) and stabilizing thereafter. Saccharase and maltase activities did not differ significantly between groups, whereas lactase showed a significant reduction in total (TA) and specific activity (SA) in the anemic animals starting on the 21st day of the study. Median lactase TA for the C and E groups was 2.27 and 1.25 U on the 21st day, 2.87 and 1.88 U on the 28th day, and 4.20 and 1.59 U on the 35th day, respectively. Median lactase SA was 0.31 and 0.20 U/g wet weight on the 21st day, 0.39 and 0.24 U/g wet weight on the 28th day, and 0.42 and 0.23 U/g wet weight on the 35th day, respectively. These findings suggest a relationship between the enzymatic alterations observed and both the degree and duration of the anemic process. Analysis of other studies on intestinal disaccharidases in anemia suggests that the mechanism of these changes may be functional, i.e., that the enterocytes may suffer a reduction in their ability to synthesize these enzymes.

Psychometric properties of the Portuguese version of the State-Trait Anxiety Inventory applied to college students: factor analysis and relation to the Beck Depression Inventory

The psychometric properties of the Portuguese version of the trait form of the State-Trait Anxiety Inventory (STAI-T) and its relation to the Beck Depression Inventory (BDI) were evaluated in a large Brazilian college student sample containing 845 women and 235 men. STAI-T scores tended to be higher for women, singles, those who work, and subjects under 30 years. Factor analysis of the STAI-T for total sample and by gender yielded two factors: the first representing a mood dimension and the second being related to worrying or cognitive aspects of anxiety. In order to study the relation between anxiety and depression measures, factor analysis of the combination of the 21 BDI items and the 20 STAI-T items was also carried out. The analysis resulted in two factors that were analyzed according to the tripartite model of anxiety and depression. Most of the BDI items (measuring positive affectivity and nonspecific symptoms of depression) were loaded on the first factor and four STAI-T items that measure positive affectivity. The remaining STAI-T items, all of them measuring negative affect, remained in the second factor. Thus, factor 1 represents a depression dimension and factor 2 measures a mood-worrying dimension. The findings of this study suggest that, although widely used as an anxiety scale, the STAI-T in fact measures mainly a general negative affect.

Photic driving in the electroencephalogram of children and adolescents: harmonic structure and relation to the resting state

In order to identify latent bioelectrical oscillators, 15 normal subjects (aged 9-17 years, 8 males, 7 females) were subjected to intermittent photic stimulation. The EEG amplitude spectra corresponding to the 11 fixed frequencies of stimulation presented (3-24 Hz) were combined to form "profiles" of the driving reaction in the right occipital area. The driving response varied with frequency, and was demonstrable in 70-100% of cases (using as criterion peak amplitudes 20% larger than those of the neighbors). The strongest responses were observed at the frequency closest to the alpha peak of the resting EEG. A secondary profile maximum was in the theta band. In 10 subjects, this maximum exceeded half the alpha peak (with an average of 72.4% of the alpha peak), while in the resting spectra, theta amplitudes were much lower than the alpha maxima. This responsiveness in theta activity seems to be characteristic of prepubertal and pubertal subjects. The profiles and resting EEG spectra showed a highly significant Pearson's correlation, with the peak in the theta band of the profiles being the main difference observed between them. The correlation coefficient was significantly correlated with the ratio of the maxima in the theta and alpha bands (R = -0.77, P<0.001). The correlation coefficient between profile and resting spectrum may be a useful indicator in screening methods used to reveal latent cerebral oscillators. Profiles for the second and third harmonics were correlated with those of the first harmonic (fundamental frequency), when considering the corresponding EEG frequencies. Peak frequencies in all three profiles were close to those of the individual's background alpha rhythm, and peak amplitudes in higher harmonics were not much lower than those of the fundamental frequency (mean values of 84 and 63%, for second and third harmonics, respectively).

The attentional modulation of the flash-lag effect

If a dot is flashed in perfect alignment with a pair of dots rotating around the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dot (flash-lag effect). This perceptual effect has been interpreted to result from the perceptual extrapolation of the moving dots, the differential visual latencies between flashing and moving stimuli, as well as the modulation of attentional mechanisms. Here we attempted to uncouple the attentional effects brought about by the spatial predictability of the flashing dot from the sensory effects dependent on its visual eccentricity. The stimulus was a pair of dots rotating clockwise around the fixation point. Another dot was flashed at either the upper right or the lower left of the visual field according to three separate blocked situations: fixed, alternate and random positions. Twenty-four participants had to judge, in all three situations, the location of the rotating dots in relation to the imaginary line connecting the flashing dot and the fixation point at the moment the dot was flashed. The flash-lag effect was observed in all three situations, and a clear influence of the spatial predictability of the flashing dot on the magnitude of the perceptual phenomenon was revealed, independently of sensory effects related to the eccentricity of the stimulus in the visual field. These findings are consistent with our proposal that, in addition to sensory factors, the attentional set modulates the magnitude of the differential latencies that give rise to the flash-lag phenomenon.

Changes in endogenous tissue glutathione level in relation to murine ascites tumor growth and the anticancer activity of cisplatin

Changes in glutathione levels were determined in tissues of 11- to 12-week-old Swiss albino mice at different stages of Dalton's lymphoma tumor growth and following cisplatin (8 mg/kg body weight, ip) treatment for 24-96 h, keeping 4-5 animals in each experimental group. Glutathione levels increased in spleen of tumor-bearing compared to normal mice (9.95 ± 0.14 vs 7.86 ± 1.64 µmol/g wet weight, P<=0.05) but decreased in blood (0.64 ± 0.10 vs 0.85 ± 0.09 mg/ml) and testes (9.28 ± 0.15 vs 10.16 ± 0.28 µmol/g wet weight, P<=0.05). Dalton's lymphoma cells showed an increase in glutathione concentration (4.43 ± 0.26 µmol/g wet weight) as compared to splenocytes, their normal counterpart (3.62 ± 0.41 µmol/g wet weight). With the progression of tumor in mice, glutathione levels decreased significantly in testes (~10%) and bone marrow cells (~13%) while they increased in Dalton's lymphoma cells (28-46%) and spleen (15-27%). Glutathione levels in kidney, Dalton's lymphoma cells and bone marrow cells (8.50 ± 1.22, 4.43 ± 0.26 and 3.28 ± 0.17 µmol/g wet weight, respectively) decreased significantly (6.04 ± 0.42, 3.51 ± 0.32 and 2.17 ± 0.14 µmol/g wet weight, P<=0.05) after in vivo cisplatin treatment for 24 h. Along with a decrease in glutathione level, the glutathione-S-transferase (GST) activity also decreased by 60% in tumor cells after cisplatin treatment. The elevated drug uptake by the tumor cells under the conditions of reduced glutathione concentration and GST activity after treatment could be an important contributory factor to cisplatin's anticancer activity leading to tumor regression. Furthermore, lower doses of cisplatin in combination with buthionine sulfoximine (an inhibitor of glutathione synthesis) may be useful in cancer chemotherapy with decreased toxicity in the host.

Statistical segmentation methods and color variance analysis of retinal images

In this research, the effectiveness of Naive Bayes and Gaussian Mixture Models classifiers on segmenting exudates in retinal images is studied and the results are evaluated with metrics commonly used in medical imaging. Also, a color variation analysis of retinal images is carried out to find how effectively can retinal images be segmented using only the color information of the pixels.

Environmental color affects Nile tilapia reproduction

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 ± 0.45 cm) and 3 females (10.78 ± 0.45 cm) each. After assignment to the respective environmental color (similar luminosity = 100 to 120 Lux), the animals were observed until reproduction (identified by eggs in the female's mouth) or up to 10 days after the first nest building. Photoperiod was from 6:00 h to 18:00 h every day. Food was offered in excess once a day and water quality was similar among aquaria. Daily observations were made at 8:00, 11:00, 14:00 and 17:00 h regarding: a) latency to the first nest, b) number of nests, c) gravel weight removed (the male excavates the nest in the bottom of the aquarium), d) nest area, and e) mouthbrooding incubation (indication of reproduction). The proportion of reproducing fish was significantly higher (6 of 13) in the group exposed to the blue color compared the group exposed to the white color (1 of 12; Goodman's test of proportions). Moreover, males under blue light removed significantly larger masses of gravel (blue = 310.70 ± 343.50 g > white = 130.38 ± 102.70 g; P = 0.01) and constructed wider nests (blue = 207.93 ± 207.80 cm² > white = 97.68 ± 70.64 cm²; P = 0.03) than the control (white). The other parameters did not differ significantly between light conditions. We concluded that reproduction in the presence of blue light was more frequent and intense than in the presence of white light.