Computadores em educação química: estrutura atômica e tabela periódica

In this paper we discuss an approach for two initial topics in Chemistry: atomic structure and periodic table. The focus of this approach is the use of educational software resources in the perspective of teacher's formation.

A dinâmica de analisar livros didáticos com os professores de química

This work evidences a survey conducted during a teacher professional qualification in Rio Grande do Sul, Brazil. This survey analysed the textbooks used by these teachers. The dynamics consisted of choosing the analytic criteria used by teachers, and adding new criteria for examining their difficulties and ways to choose textbooks. This article emphasises the problematics and difficulties teachers have to make choices and their loss of skills and authority to consider these books more profoundly.

Estudo do estado fundamental de aglomerados de silício via redes neurais

We introduce a global optimization method based on the cooperation between an Artificial Neural Net (ANN) and Genetic Algorithm (GA). We have used ANN to select the initial population for the GA. We have tested the new method to predict the ground-state geometry of silicon clusters. We have described the clusters as a piling of plane structures. We have trained three ANN architectures and compared their results with those of pure GA. ANN strongly reduces the total computational time. For Si10, it gained a factor of 5 in search speed. This method can be easily extended to other optimization problems.

As percepções dos professores de química geral sobre a seleção e a organização conceitual em sua disciplina

The teaching of general chemistry involves both the choice and the organization of its concepts. Although College Teachers make their choices, frequently the text books play an important role in this selection. In the present project we intend to show what are Teachers' perceptions of conceptual organization and selection as well as their perceptions of how to teach general chemistry. This demonstration is carried out through the use of metaphors from new information technologies.

Multicointegration, polynomial cointegration and I(2) cointegration with structural breaks. An application to the sustainability of the US external deficit

In this paper we model the multicointegration relation, allowing for one structural break. Since multicointegration is a particular case of polynomial or I(2) cointegration, our proposal can also be applied in these cases. The paper proposes the use of a residualbased Dickey-Fuller class of statistic that accounts for one known or unknown structural break. Finite sample performance of the proposed statistic is investigated by using Monte Carlo simulations, which reveals that the statistic shows good properties in terms of empirical size and power. We complete the study with an empirical application of the sustainability of the US external deficit. Contrary to existing evidence, the consideration of one structural break leads to conclude in favour of the sustainability of the US external deficit.

Another Look at the Null of Stationary Real Exchange Rates: Panel Data with Structural Breaks and Cross-section Dependence

This paper re-examines the null of stationary of real exchange rate for a panel of seventeen OECD developed countries during the post-Bretton Woods era. Our analysis simultaneously considers both the presence of cross-section dependence and multiple structural breaks that have not received much attention in previous panel methods of long-run PPP. Empirical results indicate that there is little evidence in favor of PPP hypothesis when the analysis does not account for structural breaks. This conclusion is reversed when structural breaks are considered in computation of the panel statistics. We also compute point estimates of half-life separately for idiosyncratic and common factor components and find that it is always below one year.

Panel Data Stochastic Convergence Analysis of the Mexican Regions

The stochastic convergence amongst Mexican Federal entities is analyzed in panel data framework. The joint consideration of cross-section dependence and multiple structural breaks is required to ensure that the statistical inference is based on statistics with good statistical properties. Once these features are accounted for, evidence in favour of stochastic convergence is found. Since stochastic convergence is a necessary, yet insufficient condition for convergence as predicted by economic growth models, the paper also investigates whether-convergence process has taken place. We found that the Mexican states have followed either heterogeneous convergence patterns or divergence process throughout the analyzed period.

Neurocognition in schizophrenia: a study of the productivity and visibility of spanish authors

This paper provides a map of the scientific productivity of authors affiliated to a Spanish institution and who have addressed one of the most important current topics in schizophrenia: The study of cognitive performance. A search of the Web of Science yielded 125 articles that met the inclusion criteria. In order to provide a comprehensive overview of scientific productivity, we examine several bibliometric indicators, concerning both productivity and impact or visibility. The analysis also focuses on qualitative aspects of key theoretical importance, such as the kinds of cognitive functions that are most often assessed and the tests most widely used to evaluate them in clinical practice. The study shows that interest in the subject of cognitive function in schizophrenia has increased considerably in Spain since the beginning of this century. The results also highlight the need to standardize the type of tests to be used in the cognitive assessment of patients with schizophrenia.

HIV-1 immune activation induces siglec-1 expression and enhances viral trans-infection in blood and tissue myeloid cells

Background: Myeloid cells are key players in the recognition and response of the host against invading viruses. Paradoxically, upon HIV-1 infection, myeloid cells might also promote viral pathogenesis through trans-infection, a mechanism that promotes HIV-1 transmission to target cells via viral capture and storage. The receptor Siglec-1 (CD169) potently enhances HIV-1 trans-infection and is regulated by immune activating signals present throughout the course of HIV-1 infection, such as interferon α (IFNα). Results: Here we show that IFNα-activated dendritic cells, monocytes and macrophages have an enhanced ability to capture and trans-infect HIV-1 via Siglec-1 recognition of viral membrane gangliosides. Monocytes from untreated HIV-1-infected individuals trans-infect HIV-1 via Siglec-1, but this capacity diminishes after effective antiretroviral treatment. Furthermore, Siglec-1 is expressed on myeloid cells residing in lymphoid tissues, where it can mediate viral trans-infection. Conclusions: Siglec-1 on myeloid cells could fuel novel CD4+ T-cell infections and contribute to HIV-1 dissemination in vivo.

Clinical usefulness of the Screen for Cognitive Impairment in Psychiatry (SCIP-S) scale in patients with type I bipolar disorder

Background: The relevance of persistent cognitive deficits to the pathogenesis and prognosis of bipolar disorders (BD) is understudied, and its translation into clinical practice has been limited by the absence of brief methods assessing cognitive status in Psychiatry. This investigation assessed the psychometric properties of the Spanish version of the Screen for Cognitive Impairment in Psychiatry (SCIP-S) for the detection of cognitive impairment in BD. Methods: After short training, psychiatrists at 40 outpatient clinics administered the SCIP three times over two weeks to a total of 76 consecutive type I BD admissions. Experienced psychologists also administered a comprehensive battery of standard neuropsychological instruments to clinical sample and 45 healthy control subjects. Results: Feasibility was supported by a brief administration time (approximately 15 minutes) and minimal scoring errors. The reliability of the SCIP was confirmed by good equivalence of forms, acceptable stability (ICC range 0.59 to 0.87) and adequate internal consistency (Chronbach's alpha of 0.74). Construct validity was granted by extraction of a single factor (accounting 52% of the variance), acceptable correlations with conventional neuropsychological instruments, and a clear differentiation between bipolar I and normal samples. Efficiency was also provided by the adequate sensitivity and specificity. Limitations: The sample size is not very large. The SCIP and the neurocognitive battery do not cover all potentially relevant cognitive domains. Also, sensitivity to change remains unexplored. Conclusion: With minimal training, physicians obtained a reliable and valid estimate of cognitive impairment in approximately 15 minutes from an application of the SCIP to type I BD patients.

Clinical usefulness of the Screen for Cognitive Impairment in Psychiatry (SCIP-S) scale in patients with type I bipolar disorder

Background: The relevance of persistent cognitive deficits to the pathogenesis and prognosis of bipolar disorders (BD) is understudied, and its translation into clinical practice has been limited by the absence of brief methods assessing cognitive status in Psychiatry. This investigation assessed the psychometric properties of the Spanish version of the Screen for Cognitive Impairment in Psychiatry (SCIP-S) for the detection of cognitive impairment in BD. Methods: After short training, psychiatrists at 40 outpatient clinics administered the SCIP three times over two weeks to a total of 76 consecutive type I BD admissions. Experienced psychologists also administered a comprehensive battery of standard neuropsychological instruments to clinical sample and 45 healthy control subjects. Results: Feasibility was supported by a brief administration time (approximately 15 minutes) and minimal scoring errors. The reliability of the SCIP was confirmed by good equivalence of forms, acceptable stability (ICC range 0.59 to 0.87) and adequate internal consistency (Chronbach's alpha of 0.74). Construct validity was granted by extraction of a single factor (accounting 52% of the variance), acceptable correlations with conventional neuropsychological instruments, and a clear differentiation between bipolar I and normal samples. Efficiency was also provided by the adequate sensitivity and specificity. Limitations: The sample size is not very large. The SCIP and the neurocognitive battery do not cover all potentially relevant cognitive domains. Also, sensitivity to change remains unexplored. Conclusion: With minimal training, physicians obtained a reliable and valid estimate of cognitive impairment in approximately 15 minutes from an application of the SCIP to type I BD patients.

A tabela periódica dos elementos químicos prevista por redes neurais artificiais de Kohonen

Although several chemical elements were not known by end of the 18th century, Mendeleyev came up with an astonishing achievement: the periodic table of elements. He was not only able to predict the existence of (then) new elements but also to provide accurate estimates of their chemical and physical properties. This is certainly a relevant example of the human intelligence. Here, we intend to shed some light on the following question: Can an artificial intelligence system yield a classification of the elements that resembles, in some sense, the periodic table? To achieve our goal, we have fed a self-organized map (SOM) with information available at Mendeleyev's time. Our results show that similar elements tend to form individual clusters. Thus, SOM generates clusters of halogens, alkaline metals and transition metals that show a similarity with the periodic table of elements.

Emprego de metodologia enzimática na obtenção de extratos protéicos de farinha de trigo

An enzymatic method was used for obtaining protein extracts from wheat flour using an alkaline protease. Some parameters were evaluated aiming the optimization of this method: temperature (40-50 ºC); time (2-5 h); physical treatment of the sample (no treatment, ultra-turrax/16,000 rpm/5 min and ultrasound/120 W/10 min); enzyme:substrate ratio (E:S) of 5:100 - 10:100 and concentration of wheat flour (1:3, 1:5 and 1:10 w/v). The results showed that the best condition for protein extraction was that using the sample concentration of 1:3 (w/v), ultra-turrax, E:S of 10:100, at 40 ºC, 2 h, having reached an extraction yield of 88.53%.

Noções dos futuros profissionais da Química. eixo I: liberdades e demandas da pesquisa

During the schooling process, images are constructed about research and researcher activities. Based on that, a questionnaire has been structured based on three thematic axes that tend to represent some of the discussions about the translations that integrate the scientific activity collectively: freedom and demands from research, academia as a mediator and science disclosure. The objective of the instrument was to map some notions from entrants to the graduation course in Chemistry in the metropolitan region of Porto Alegre about what, based on the contributions by Bruno Latour, was called vascularizations of research.