Differential Hypothesis Research Articles

Nonlocal theory of curved rods. 2-D, high order, Timoshenko’s and Euler-Bernoulli models

Abstract New models for plane curved rods based on linear nonlocal theory of elasticity have been developed. The 2-D theory is developed from general 2-D equations of linear nonlocal elasticity using a special curvilinear system of coordinates related to the middle line of the rod along with special hypothesis based on assumptions that take into account the fact that the rod is thin. High order theory is based on the expansion of the equations of the theory of elasticity into Fourier series in terms of Legendre polynomials. First, stress and strain tensors, vectors of displacements and body forces have been expanded into Fourier series in terms of Legendre polynomials with respect to a thickness coordinate. Thereby, all equations of elasticity including nonlocal constitutive relations have been transformed to the corresponding equations for Fourier coefficients. Then, in the same way as in the theory of local elasticity, a system of differential equations in terms of displacements for Fourier coefficients has been obtained. First and second order approximations have been considered in detail. Timoshenko’s and Euler-Bernoulli theories are based on the classical hypothesis and the 2-D equations of linear nonlocal theory of elasticity which are considered in a special curvilinear system of coordinates related to the middle line of the rod. The obtained equations can be used to calculate stress-strain and to model thin walled structures in micro- and nanoscales when taking into account size dependent and nonlocal effects.

Factor specificity and wage inequality in a developing economy: The role of technology and trade in Indian manufacturing

The wage inequality between skilled and unskilled labour has been observed to have risen in both developed and developing countries in recent years. The received explanations for this phenomenon have been mainly attributed to (1) outsourcing and (2) skilled biased technological change. However, very few of these explanations were carried out in a general equilibrium framework. In a recent paper using a general equilibrium framework with factor specificity it has been suggested that differential marginal productivity growth of skilled and unskilled labour could be a possible cause of rising wage inequality. While this is an interesting testable hypothesis, it is in essence, seems to be incomplete as it does not try to explain why the productivities of skilled and unskilled labour should move differently. In our paper, we shall try to first, examine the trend of wage inequality in Indian manufacturing and second, examine whether the productivity differential hypothesis as an explanation of rising wage inequality in India can be validated. Having done this we further try to examine the possible factors that might be affecting the marginal productivities of skilled and unskilled labour differently.

Sex and breeding status affect prey composition of Harpy Eagles Harpia harpyja

Foraging behavior may show considerable variation among population classes—such as sex and breeding class—that can be consequence of the groups’ specific constraints and roles. In raptors, differential parental roles related to foraging have been the main explanation for males being smaller than females, as smaller males have been described to be more efficient foragers. During one phase of breeding, only males forage, requiring them to feed themselves, females and young. This is expected to induce changes in foraging behavior of breeders compared to non-breeders. By comparing prey taken by floaters and breeders of Harpy Eagles (Harpia harpyja), we describe some effects of breeding and sex on the diet. Here we show that diet traits differed between male and female floaters, and between floaters and breeders. Juvenile prey was three times more common in the diet of males than that of females. Sloths were more common prey among females than among males (53 vs. 37%). Males preyed four times more on terrestrial animals than did females, and showed a greater niche width than females (6.0 vs. 3.4). The prey of breeders was smaller than that of non-breeders (on average 3.64 vs. 4.24 kg). Non-breeders had a larger niche width than breeders. Our data provide support for the hypothesis of parental role differentiation as an explanation for reversed sexual size dimorphism in raptors.

Corporate Governance and Innovation under Demand Uncertainty: A Panel Study of Korean Firms

Existing literature has identified the effects of competition and firms’ ownership and management structure on firms’ decisions to invest in innovation. We extend this literature by examining the role of market-demand uncertainty on the relationship between firm ownership, management structure and management turnover, on the one hand, and firms’ innovation on the other hand. We evaluate the effects of firms’ competitiveness, concentration of firms’ ownership, presence of foreigners among owners and on owner-appointed corporate boards of directors, management independence, and management turnover rates on firms’ patent applications under varying degrees of demand uncertainty. The validity of alternative hypotheses about management motivation - lazy manager, career concerns, prospect theory, and special East-Asian institutional constraints hypotheses - is evaluated, controlling for firms’ prior investment in innovation and firm characteristics. Unique data for 711 Korean firms and nine years, 2003-2011, are used (4,339 records). We find support for the lazy-manager hypothesis by identifying substitutability between competitive pressures and owner-manager separation in driving managers’ effort to pursue innovation. Demand uncertainty raises managers’ incentives to innovate, by increasing the potential stake from innovation and increasing the risk of default if firms fail to innovate. There is little evidence that Korean managers pursue innovation to ease their career concerns or to meet an expected performance yardstick, or that they follow an idiosyncratic East-Asian pattern. Management turnover has little effect on innovation, and firms’ existing performance increases innovation. Foreign ownership and direction, and the share of the largest firm owner have little effect on firms’ innovation.

Tropical insect diversity: evidence of greater host specialization in seed-feeding weevils.

Host specialization has long been hypothesized to explain the extraordinary diversity of phytophagous insects in the tropics. However, addressing this hypothesis has proved challenging because of the risk of over-looking rare interactions, and hence biasing specialization estimations, and the difficulties to separate the diversity component attributable to insect specialization from that related to host diversity. As a result, the host specialization hypothesis lacks empirical support for important phytophagous insect clades. Here, we test the hypothesis in a radiation of seed-feeding insects, acorn weevils (Curculio spp.), sampled in temperate and tropical regions (California and Nicaragua, respectively) with an equivalent pool of oak host species. Using DNA sequences from three low-copy genes, we delimited to species level 778 weevil larvae extracted from host seeds and assessed their phylogenetic relationships by Maximum Likelihood and Bayesian inference. We then reconstructed the oak-weevil food webs and examined differences in alpha, beta and gamma diversity using Hill numbers of effective species. We found a higher alpha, beta and gamma diversity of weevils in Nicaragua compared to California despite similar richness of host species at both local and regional level. By means of Bayesian mixed models, we also found that tropical weevil species were highly specialized both in terms of host range and interaction strength, whereas their temperate congeners had a broader taxonomic and phylogenetic host spectrum. Finally, in Nicaraguan species, larval body size was highly correlated with the size of the acorns infested, as would be expected by a greater host specialization, whereas in California this relationship was absent. Altogether, these lines of evidence support the host specialization hypothesis and suggest contrasting eco-evolutionary dynamics in tropical and temperate regions even in absence of differences in host diversity.

Beyond Risk and Protective Factors: An Adaptation-Based Approach to Resilience

How does repeated or chronic childhood adversity shape social and cognitive abilities? According to the prevailing deficit model, children from high-stress backgrounds are at risk for impairments in learning and behavior, and the intervention goal is to prevent, reduce, or repair the damage. Missing from this deficit approach is an attempt to leverage the unique strengths and abilities that develop in response to high-stress environments. Evolutionary-developmental models emphasize the coherent, functional changes that occur in response to stress over the life course. Research in birds, rodents, and humans suggests that developmental exposures to stress can improve forms of attention, perception, learning, memory, and problem solving that are ecologically relevant in harsh-unpredictable environments (as per the specialization hypothesis). Many of these skills and abilities, moreover, are primarily manifest in currently stressful contexts where they would provide the greatest fitness-relevant advantages (as per the sensitization hypothesis). This perspective supports an alternative adaptation-based approach to resilience that converges on a central question: “What are the attention, learning, memory, problem-solving, and decision-making strategies that are enhanced through exposures to childhood adversity?” At an applied level, this approach focuses on how we can work with, rather than against, these strengths to promote success in education, employment, and civic life.

Sex differences during place learning in the túngara frog

The adaptive specialization hypothesis states that sex differences in cognition are shaped by differences in cognitive demands to solve ecological problems. While it is widely accepted that female mate choice can lead to the evolution of exaggerated male traits, mate choice might also select for different cognitive abilities in males and females. In the tungara frog, Physalaemus (= Engystomops) pustulosus, males call from a fixed position in breeding ponds while females visit multiple males before returning to the preferred mate. Thus, we predicted that females have better place memory than males. We tested this prediction in a place-learning task in which the rewarded arm of a maze was associated with a visual cue. We found that females were able to use the visual cue to solve the task while males were not, even though both males and females could discriminate the cues in an optomotor test. In contrast, males attempted to solve the task using egocentric cues (remember body-turn direction) in spite of the fact that our training procedure interrupted their use of such cues. Finally, we found that males and females had similar motivation to solve the task but females showed a greater ability to inhibit incorrect responses, leading to improved learning. Our finding that females could use a visual cue to remember locations in space is consistent with the idea that place memory could improve sequential mate assessment in tungara frogs.

Domain-general Stroop Performance and Hemispheric Asymmetries: A Resting-state EEG Study.

The ability to suppress irrelevant information while executing a task, also known as interference resistance ability, is a function of pFC that is critical for successful goal-directed human behavior. In the study of interference resistance and, more generally, executive functions, two key questions are still open: Does pFC contribute to cognitive control abilities through lateralized but domain-general mechanisms or through hemispheric specialization of domain-specific processes? And what are the underlying causes of interindividual differences in executive control performance? To shed light on these issues, here we employed an interindividual difference approach to investigate whether participants' hemispheric asymmetry in resting-state electrophysiological brain dynamics may reflect their variability in domain-general interference resistance. We recorded participants' resting-state electroencephalographic activity and performed spectral power analyses on the estimated cortical source activity. To measure participants' lateralized brain dynamics at rest, we computed the right-left hemispheric asymmetry score for the β/α power ratio. To measure their domain-general interference resistance ability, verbal and spatial Stroop tasks were used. Robust correlations followed by intersection analyses showed that participants with stronger resting-state-related left-lateralized activity in different pFC regions, namely the mid-posterior superior frontal gyrus, middle and posterior middle frontal gyrus, and inferior frontal junction, were more able to inhibit irrelevant information in both domains. The present results confirm and extend previous findings showing that neurophysiological difference factors may explain interindividual differences in executive functioning. They also provide support for the hypothesis of a left pFC hemispheric specialization for domain-independent phasic cognitive control processes mediating Stroop performance.

Social personality: a more social shrew species exhibits stronger differences in personality types

Animal personalities have been studied extensively in the last decade. It is still not entirely understood, however, how different personalities evolve and persist. The social niche specialization hypothesis suggests that in group-living animals the combination of social conflicts and alternative options on how to deal with them are of key importance for the development and evolution of animal personality. Here we predicted that, following the social niche specialization hypothesis, a more social species should have more pronounced personality differences. We tested this prediction using four species of shrews that differ in ecology and sociability. Three species (Neomys fodiens, Sorex araneus and Sorex minutus) are strictly solitary outside the breeding season; the fourth species (Neomys anomalus) is intraspecifically more tolerant and able to live in groups. These four species offer a good model to assess our questions as N. anomalus can, in many other respects (e.g. body size, habitat, foraging mode), be considered as an ‘in-between’ species. We tested individuals of all species for their solitary activity and their activity and agonistic behaviour in within- and between-species dyadic encounters. We found that individuals of N. anomalus, but not the other species tested, showed consistent behavioural variation in agonistic behaviour. Consistent individual differences in activity were, however, also present in other species and activity was further correlated between the different contexts in all tested species. Finding more pronounced personality differences in N. anomalus than in the other, less sociable species supports the hypothesis that social niche specialization can influence the evolution of animal personalities.

English

This research examined how Thai undergraduates acquired English marked and unmarked fricatives in their interlanguage. It also determined what sounds the learners used to replace some fricatives and how variable they were. Based on the Markedness Differential Hypothesis (MDH), unmarked fricatives are /s/ and /f/, and marked ones are /ʃ/, /v/, /z/, /θ/, /ð/, and /ʒ/. The former are considered unmarked because they are available in Thai, whereas the latter are not. The participants included three groups: high, intermediate, and low proficiency students who were studied through three types of tasks: word list, sentence list, and oral interview. The word and sentence lists required the learners to produce the target fricatives in a formal situation, while the oral interview in a natural context. The results demonstrated that marked fricatives /v/, /z/, /θ/, /ð/, and /ʒ/ were difficult for the participants. Only the advanced informants could acquire unmarked /s/ and /f/ as well as marked /ʃ/ both initially and finally. According to the MDH, the learners produced /s/, /f/, and /ʃ/ before marked /v/, /z/, /θ/, /ð/, and /ʒ/. They also appeared to produce various substitutions for the problematic sounds. Plausible explanations to account for the Thai learners’ difficulty of English fricatives involve the first language (L1) transfer, distribution of a particular sound, voicing, systematic variability, and design of a task. In pronunciation classes, teachers or educators may design tasks appropriate for their learners and employ strategies that suit their learning style preferences. Keywords: English fricatives; interlanguage; L2 phonology; markedness; variability DOI: http://doi.org/10.17576/3L-2017-2301-02

A diferenciação cognitiva na infância: um estudo de perfis cognitivos aos 5, 7 e 9 anos

Resumo No seio do debate sobre se a inteligência é mais bem definida por um fator geral ou por aptidões específicas, ganha relevância a hipótese da diferenciação cognitiva. Análises recentes enfatizam o interesse dessa questão para a investigação e alertam para a relevância das suas implicações na área educativa. Este estudo analisou a possibilidade de a diferenciação das aptidões cognitivas ocorrer já na infância e também o efeito moderador do Quociente de Inteligência na magnitude da relação entre as habilidades cognitivas. Aplicou-se uma bateria de provas que avaliam várias funções cognitivas a uma amostra de 231 crianças com 5, 7 e 9 anos, distribuídas por três grupos de desempenho cognitivo. Os resultados de uma análise de clusters hierárquica e de uma análise de variância apontam para a não diferenciação das funções cognitivas na infância. Contudo, uma análise mais cuidadosa aponta para alguma diferenciação suportada pela hete-rogeneidade dos perfis cognitivos junto dos alunos com Quociente de Inteligência elevado.

Social Support, Loyalty to Delinquent Peers, and Offending: An Elaboration and Test of the Differential Social Support Hypothesis

ABSTRACTWhile most research focuses on the positive effects of social support on adolescent development, Cullen hypothesizes that social support may promote crime and delinquency under certain conditions. Specifically, when social support is derived from deviant sources, it may promote offending behavior. In this study, we test an elaborated version of this “differential social support” hypothesis. The results indicate that, among adolescents who associate with delinquent peers, peer social support is associated with an increase in delinquent behavior. These findings highlight the potential “dark side” of social support. Implications for criminological theory and crime control policy are discussed.

Micropolar curved rods. 2-D, high order, Timoshenko’s and Euler-Bernoulli models

AbstractNew models for micropolar plane curved rods have been developed. 2-D theory is developed from general 2-D equations of linear micropolar elasticity using a special curvilinear system of coordinates related to the middle line of the rod and special hypothesis based on assumptions that take into account the fact that the rod is thin.High order theory is based on the expansion of the equations of the theory of elasticity into Fourier series in terms of Legendre polynomials. First stress and strain tensors,vectors of displacements and rotation and body force shave been expanded into Fourier series in terms of Legendre polynomials with respect to a thickness coordinate.Thereby all equations of elasticity including Hooke’s law have been transformed to the corresponding equations for Fourier coefficients. Then in the same way as in the theory of elasticity, system of differential equations in term of displacements and boundary conditions for Fourier coefficients have been obtained. The Timoshenko’s and Euler-Bernoulli theories are based on the classical hypothesis and 2-D equations of linear micropolar elasticity in a special curvilinear system. The obtained equations can be used to calculate stress-strain and to model thin walled structures in macro, micro and nano scale when taking in to account micropolar couple stress and rotation effects.

Couple stress theory of curved rods. 2-D, high order, Timoshenko’s and Euler-Bernoulli models

AbstractNew models for plane curved rods based on linear couple stress theory of elasticity have been developed.2-D theory is developed from general 2-D equations of linear couple stress elasticity using a special curvilinear system of coordinates related to the middle line of the rod as well as special hypothesis based on assumptions that take into account the fact that the rod is thin. High order theory is based on the expansion of the equations of the theory of elasticity into Fourier series in terms of Legendre polynomials. First, stress and strain tensors, vectors of displacements and rotation along with body forces have been expanded into Fourier series in terms of Legendre polynomials with respect to a thickness coordinate.Thereby, all equations of elasticity including Hooke’s law have been transformed to the corresponding equations for Fourier coefficients. Then, in the same way as in the theory of elasticity, a system of differential equations in terms of displacements and boundary conditions for Fourier coefficients have been obtained. Timoshenko’s and Euler-Bernoulli theories are based on the classical hypothesis and the 2-D equations of linear couple stress theory of elasticity in a special curvilinear system. The obtained equations can be used to calculate stress-strain and to model thin walled structures in macro, micro and nano scales when taking into account couple stress and rotation effects.

Cerebral laterality for language is related to adult salivary testosterone levels but not digit ratio (2D:4D) in men: A functional transcranial Doppler ultrasound study

The adequacy of three competing theories of hormonal effects on cerebral laterality are compared using functional transcranial Doppler sonography (fTCD). Thirty-three adult males participated in the study (21 left-handers). Cerebral lateralization was measured by fTCD using an extensively validated word generation task. Adult salivary testosterone (T) and cortisol (C) concentrations were measured by luminescence immunoassay and prenatal T exposure was indirectly estimated by the somatic marker of 2nd to 4th digit length ratio (2D:4D). A significant quadratic relationship between degree of cerebral laterality for language and adult T concentrations was observed, with enhanced T levels for strong left hemisphere dominance and strong right hemisphere dominance. No systematic effects on laterality were found for cortisol or 2D:4D. Findings suggest that higher levels of T are associated with a relatively attenuated degree of interhemispheric sharing of linguistic information, providing support for the callosal and the sexual differentiation hypotheses rather than the Geschwind, Behan and Galaburda (GBG) hypothesis.

Sex differences and violence among primary school students

Sex differences and violence among primary school students

Lagrange’s theorem, convex functions and Gauss map

As one of the main results we prove that if f has Lagrange unique property then f is strictly convex or concave (we do not assume continuity of the derivative), Theorem 2.1. We give two different proofs of Theorem 2.1 (one mainly using Lagrange theorem and the other using Darboux theorem). In addition, we give a few characterizations of strictly convex curves, in Theorem 3.5. As an application of it, we give characterization of strictly convex planar curves, which have only tangents at every point, by injective of the Gauss map. Also without the differentiability hypothesis we get the characterization of strictly convex or concave functions by two points property, Theorem 4.2.

Checking the Alleged “Incompatibility of the Relic Dark Energy Hypothesis” with Physically Admissible Solutions to the Cosmic Ray Problem of Doubly Special Relativity

We offer evidence that the Trans Plankian hypothesis about Dark energy is incompatible with necessary and sufficient conditions for solving the cosmic ray problem along the lines presented by Magueijo et al. We can obtain conditions for a dispersion relationship congruent with the Trans Planckian hypothesis only if we cease trying to match cosmic ray data which is important in investigating Doubly Special Relativity. This leads us to conclude that the Trans Planckian hypothesis is inconsistent with respect to current astrophysical data when modeled by Doubly Special Relativity and needs to be seriously revised. Or the Doubly Special Relativity Hypothesis needs to be abandoned.

Does Cerebral Hemispheric Laterality Control Swallow Performance?

Objectives It is well established that the brainstem regulates the act of swallow. However, the role of cortex and its influence on swallowing are still a question. Hence, the present study aimed to investigate if cerebral hemispheric laterality controls swallow activity. Methods Thirty normal right handed participants were subjected to time test of swallow using 100 ml of water. Dual paradigm was used to investigate hemispheric laterality for swallowing which involved listening to the speech or music stimuli presented binaurally while swallowing. The clinician measured total time taken and hyolaryngeal movement simultaneously which was used to calculate volume/time, volume/swallow, and time/swallow on an offline basis. Results Results revealed that swallow performance decreased with the dual task paradigm compared to baseline swallow. These results are suggestive of cortex playing a role during swallowing in the dual task paradigm. Moreover, quantitative parameters like volume/swallow and volume/time were affected more when speech was competing with swallowing. However, music exerted greater interference over the speech for time/swallow. Conclusions These results suggests that there exists differential cue lateralization hypothesis which means volume related parameters are controlled by left hemisphere and time related swallowing parameters are controlled at the right hemisphere.

An empirical examination of the strength differential hypothesis in cyberbullying behavior.

An empirical examination of the strength differential hypothesis in cyberbullying behavior.