A phylogenetic comparative analysis on the evolution of sequential hermaphroditism in seabreams (Teleostei : Sparidae)

The Sparids are an ideal group of fish in which to study the evolution of sexual systems since they exhibit a great sexual diversity, from gonochorism (separate sexes) to protandrous (male-first) and protogynous (female-first) sequential hermaphroditism (sex-change). According to the size-advantage model (SAM), selection should favour sex change when the second sex achieves greater reproductive success at a larger body size than the first sex. Using phylogenetic comparative methods and a sample of 68 sparid species, we show that protogyny and protandry evolve from gonochorism but evolutionary transitions between these two forms of sequential hermaphroditism are unlikely to happen. Using male gonadosomatic index (GSI) as a measure of investment in gametes and proxy for sperm competition, we find that, while gonochoristic and protogynous species support the predictions of SAM, protandrous species do not, as they exhibit higher GSI values than expected even after considering mating systems and spawning modes. We suggest that small males of protandrous species have to invest disproportionally more in sperm production than predicted not only when spawning in aggregations with high levels of sperm competition, but also when spawning in pairs due to the need to fertilize highly fecund females, much larger than themselves. We propose that this compensatory mechanism, together with Bateman’s principles in sequential hermaphrodites, should be formally incorporated in the SAM

Ultra-dense phosphorus in germanium delta-doped layers

Phosphorus (P) in germanium (Ge) delta-doped layers are fabricated in ultra-high vacuum by adsorption of phosphine molecules onto an atomically flat clean Ge(001) surface followed by thermal incorporation of P into the lattice and epitaxial Ge overgrowth by molecular beam epitaxy. Structural and electrical characterizations show that P atoms are confined, with minimal diffusion, into an ultra-narrow 2-nm-wide layer with an electrically-active sheet carrier concentration of 4x10^13 cm-2 at 4.2 K. These results open up the possibility of ultra-narrow source/drain regions with unprecedented carrier densities for Ge n-channel field effect transistors

Phylogenetic signal in amphibian sensitivity to copper sulfate relative to experimental temperature

The release of large quantities of chemicals into the environment represents a major source of environmental disturbance. In recent years, the focus of ecotoxicology has shifted from describing the effects of chemical contaminants on individual species to developing more integrated approaches for predicting and evaluating long term effects of chemicals across species and ecosystems. Traditional ecotoxicology is typically based on data of sensitivity of a few surrogate species to a contaminant and often considers little variability in chemical sensitivity within and among taxonomic groups. This approach assumes that evolutionary history and phylogenetic relatedness among species have little or no impact on species’ sensitivity to chemical compounds. Few studies have tested this assumption. Using phylogenetic comparative methods and published data for amphibians, we show that sensitivity to copper sulfate, a commonly used pesticide, exhibits a strong phylogenetic signal when controlling for experimental temperature. Our results indicate that evolutionary history needs to be accounted for to make accurate predictions of amphibian sensitivity to this contaminant under different temperature scenarios. Since physiological and metabolic traits showing high phylogenetic signal likely underlie variation in species sensitivity to chemical stressors, future studies should evaluate and predict species vulnerability to pollutants using evolutionarily informed approaches

Pbx loss in cranial neural crest, unlike in epithelium, results in cleft palate only and a broader midface.

Orofacial clefting represents the most common craniofacial birth defect. Cleft lip with or without cleft palate (CL/P) is genetically distinct from cleft palate only (CPO). Numerous transcription factors (TFs) regulate normal development of the midface, comprising the premaxilla, maxilla and palatine bones, through control of basic cellular behaviors. Within the Pbx family of genes encoding Three Amino-acid Loop Extension (TALE) homeodomain-containing TFs, we previously established that in the mouse, Pbx1 plays a preeminent role in midfacial morphogenesis, and Pbx2 and Pbx3 execute collaborative functions in domains of coexpression. We also reported that Pbx1 loss from cephalic epithelial domains, on a Pbx2- or Pbx3-deficient background, results in CL/P via disruption of a regulatory network that controls apoptosis at the seam of frontonasal and maxillary process fusion. Conversely, Pbx1 loss in cranial neural crest cell (CNCC)-derived mesenchyme on a Pbx2-deficient background results in CPO, a phenotype not yet characterized. In this study, we provide in-depth analysis of PBX1 and PBX2 protein localization from early stages of midfacial morphogenesis throughout development of the secondary palate. We further establish CNCC-specific roles of PBX TFs and describe the developmental abnormalities resulting from their loss in the murine embryonic secondary palate. Additionally, we compare and contrast the phenotypes arising from PBX1 loss in CNCC with those caused by its loss in the epithelium and show that CNCC-specific Pbx1 deletion affects only later secondary palate morphogenesis. Moreover, CNCC mutants exhibit perturbed rostro-caudal organization and broadening of the midfacial complex. Proliferation defects are pronounced in CNCC mutants at gestational day (E)12.5, suggesting altered proliferation of mutant palatal progenitor cells, consistent with roles of PBX factors in maintaining progenitor cell state. Although the craniofacial skeletal abnormalities in CNCC mutants do not result from overt patterning defects, osteogenesis is delayed, underscoring a critical role of PBX factors in CNCC morphogenesis and differentiation. Overall, the characterization of tissue-specific Pbx loss-of-function mouse models with orofacial clefting establishes these strains as unique tools to further dissect the complexities of this congenital craniofacial malformation. This study closely links PBX TALE homeodomain proteins to the variation in maxillary shape and size that occurs in pathological settings and during evolution of midfacial morphology

Phonological remediation program in students with developmental dyslexia

BACKGROUND: program for phonological remediation in developmental dyslexia. AIM: to verify the efficacy of a program for phonological remediation in students with developmental dyslexia. Specific goals of this study involved the comparison of the linguistic-cognitive performance of students with developmental dyslexia with that of students considered good readers; to compare the results obtained in pre and post-testing situations of students with dyslexia who were and were not submitted to the program; and to compare the results obtained with the phonological remediation program in students with developmental dyslexia to those obtained in good readers. METHOD: participants of this study were 24 students who were divided as follows: Group I (GI) was divided in two other groups - GIe with 6 students with developmental dyslexia who were submitted to the program; and GIc with 6 students with developmental dyslexia who were not submitted to the program; Group II (GII) was also divided in two other groups - GIIe with 6 good readers who were submitted to the program, and GIIc with 6 good readers who were not submitted to the program. The phonological remediation program (Gonzalez & Rosquete, 2002) was developed in three stages: pre-testing, training and post-testing. RESULTS: results indicate that GI presented a lower performance in phonological skills, reading and writing when compared to GII in the pre-testing situation. However, GIe presented a similar performance to that of GII in the post-testing situation, indicating the effectiveness of the phonological remediation program in students with developmental dyslexia. CONCLUSION: this study made evident the effectiveness of the phonological remediation program in students with developmental dyslexia.TEMA: programa de remediação fonológica na dislexia do desenvolvimento. OBJETIVOS: verificar a eficácia do programa de remediação fonológica em escolares com dislexia do desenvolvimento. Dentre os objetivos específicos, o estudo visou comparar o desempenho cognitivo-lingüístico de escolares com dislexia do desenvolvimento com escolares bons leitores; comparar os achados dos procedimentos de avaliação utilizados na pré e pós-testagem em escolares com dislexia submetidos e não submetidos ao programa, e comparar os achados do programa de remediação fonológica em escolares com dislexia e escolares bons leitores submetidos ao programa de remediação. MÉTODO: participaram deste estudo 24 escolares, sendo o grupo I (GI) subdivido em: GIe composto por seis escolares com dislexia do desenvolvimento submetidos ao programa, e GIc, composto por seis escolares com dislexia do desenvolvimento não submetidos ao programa. O grupo II (GII), subdividido em GIIe, composto por seis escolares bons leitores submetidos à remediação e GIIc, composto por seis escolares bons leitores não submetidos à remediação. Foi realizado programa de remediação fonológica (Gonzalez e Rosquete, 2002) em três etapas: pré-testagem, treino, pós-testagem. RESULTADOS: os resultados deste estudo revelaram que o GI apresentou desempenho inferior em habilidade fonológica, de leitura e escrita do que o GII em situação de pré-testagem. Entretanto, o GIe apresentou desempenho semelhante ao GII em situação de pós-testagem, evidenciando a eficácia do programa de remediação com habilidades fonológicas em escolares com dislexia do desenvolvimento. CONCLUSÃO: o estudo evidenciou a eficácia do treinamento com as habilidades fonológicas para os escolares com dislexia.313

Comparison of performance in metalinguistic tasks among students with and without risk of dyslexia

Introduction: Studies on students at risk for dyslexia have increased  as well as the interest in verifying whether tasks involving a phonological basis can favor the performance of these students in the initial literacy process.Objective:Evaluate the performance of students with and without risk of dyslexia in metalinguistic tasks.Methods: Participants of this study were 40 students, aged between 5-6 years, enrolled in the 1st year of elementary school, divided into two groups, GI: composed of 20 students without risk of dyslexia and GII: composed of 20 students at risk of dyslexia, both groups were submitted to the Evaluation Cognitive Linguistic Skills Protocol - collective and individual version (adapted), and phonological intervention composed of tasks of relation letter/sound alphabet in sequence and in random order, rhyme, identification and manipulation of words, identification and production of syllables, syllabic segmentation and analysis, identification and phonemic segmentation, substitution, synthesis, analysis and phonemic discrimination. Results: Indicated that the students from GI and GII showed statistically superior performance in the post testing compared to the performance obtained in the pre testing.Conclusion: The students at risk of dyslexia showed an increase in the mean of performance after the intervention, however, when compared with the performance of the students without risk for dyslexia, they presented inferior performance, indicating that, even after have underwent  to the intervention, they did not reach the mean of performance of students without risk for dyslexia in metalinguistic tests

Use of technological tools to evaluate handwriting production of the alphabet and pseudocharacters by Brazilian students

OBJECTIVE: This study aimed to characterize and compare the handwriting performance of Brazilian students from the 3rd to the 5th grade level of elementary school I with a computerized instrument that allowed the real performance to be observed during the execution of the handwriting. METHODS: Ninety-five students, aged 8 years to 11 years and 11 months, were assigned the production tasks of handwriting letters and pseudocharacters to assess the variables of latency, letter duration production and movement fluency. The stimulus presentation and the analysis of the movements were analyzed by Ductus software. RESULTS: In relation to the writing duration, latency and fluency of the alphabet letters, there was a diminution of values from the 3rd to 5th grade. For the comparison between alphabet and pseudocharacter latency, the results indicated a difference between the alphabet letter and its corresponding pseudocharacter, with greater latency for the pseudocharacter. This finding suggests that a motor sequence has not been established, so it cannot be assumed that the production of the alphabet letters was automatic. CONCLUSION: The results of this study make it possible to verify the interaction failures between the central and peripheral processes, with progression between the 3rd and 5th grade. It also highlights the influence of the lack of systematized teaching of the tracing of letters for Brazilian students since proficiency in calligraphy is critically linked to academic performance. These findings provide a great contribution to Brazilian educational psychology and reflect both educational and clinical practices

Light effective hole mass in undoped Ge/SiGe quantum wells

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities ($2.0-11\times10^{11}$ cm$^{-2}$) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of $0.061m_e$ at a density of $2.2\times10^{11}$ cm$^{-2}$. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective mass of $\sim0.05m_e$ at zero density, the lightest effective mass for a planar platform that demonstrated spin qubits in quantum dots

Fast life history traits promote invasion success in amphibians and reptiles

Competing theoretical models make different predictions on which life history strategies facilitate growth of small populations. While ‘fast’ strategies allow for rapid increase in population size and limit vulnerability to stochastic events, ‘slow’ strategies and bet-hedging may reduce variance in vital rates in response to stochasticity. We test these predictions using biological invasions since founder alien populations start small, compiling the largest dataset yet of global herpetological introductions and life history traits. Using state-of-the-art phylogenetic comparative methods, we show that successful invaders have fast traits, such as large and frequent clutches, at both establishment and spread stages. These results, together with recent findings in mammals and plants, support ‘fast advantage’ models and the importance of high potential population growth rate. Conversely, successful alien birds are bet-hedgers. We propose that transient population dynamics and differences in longevity and behavioural flexibility can help reconcile apparently contrasting results across terrestrial vertebrate classes

Influence of encapsulation temperature on Ge:P delta-doped layers

We present a systematic study of the influence of the encapsulation temperature on dopant confinement and electrical properties of Ge:P delta-doped layers. For increasing growth temperature we observe an enhancement of the electrical properties accompanied by an increased segregation of the phosphorous donors, resulting in a slight broadening of the delta-layer. We demonstrate that a step-flow growth achieved at 530 C provides the best compromise between high crystal quality and minimal dopant redistribution, with an electron mobility ~ 128 cm^2/Vs at a carrier density 1.3x10^14 cm-2, and a 4.2 K phase coherence length of ~ 180 nm.Comment: Phys. Rev. B, in press (2009