Energetics and stability of vacancies in carbon nanotubes

In this work we present ab initio calculations of the formation energies and stability of different types of multi-vacancies in carbon nanotubes. We demonstrate that, as in the case of graphene, the reconstruction of the defects has drastic effects on the energetics of the tubes. In particular, the formation of pentagons eliminates the dangling bonds thus lowering the formation energy. This competition leads to vacancies having an even number of carbon atoms removed to be more stable. Finally the appearance of magic numbers indicating more stable defects can be represented by a model for the formation energies that is based on the number of dangling bonds of the unreconstructed system, the pentagons and the relaxation of the final form of the defect formed after the relaxation

Algebraic tools for the study of quaternionic behavioral systems

In this paper we study behavioral systems whose trajectories are given as solutions of quaternionic difference equations. As happens in the commutative case, it turns out that quaternionic polynomial matrices play an important role in this context. Therefore we pay special attention to such matrices and derive new results concerning their Smith form. Based on these results, we obtain a characterization of system theoretic properties such as controllability and stability of a quaternionic behavior

High school biology textbooks: results from PNLEM/2007

Em 2005, os livros didáticos de Biologia do ensino médio publicados no Brasil foram avaliados, como parte do Programa Nacional do Livro para o Ensino Médio (PNLEM). Neste artigo, relatamos resultados dessa avaliação. Os critérios e o processo de avaliação são apresentados de modo detalhado, bem como os principais problemas das obras não-recomendadas para compra pelo MEC e os principais aspectos positivos das obras recomendadas. Das 18 obras submetidas à avaliação, nove satisfizeram os critérios mínimos de qualidade para aprovação. Sete obras didáticas excluídas apresentaram problemas em todas as classes de critérios de avaliação. Todas as nove obras excluídas exibiram problemas relativos à correção e adequação conceituais, e à precisão da informação básica fornecida. As qualidades mais frequentes nas obras recomendadas diziam respeito à adequação metodológica e à construção do conhecimento. Não encontramos evidências claras de que a frequência de escolha pelos professores do ensino médio refletiu a qualidade dos itens avaliados, conforme estabelecida pela equipe que analisou as obras.In 2005, Brazilian Biology high school textbooks were evaluated as part of the National Program for the High School Textbook (PNLEM). In this paper, we report results of this evaluation. The evaluation criteria and processes are presented in a detailed manner, as well as the main flaws found in the textbooks not recommended to be bought by the Ministry of Education and the main positive aspects of the approved materials. Nine out of 18 textbooks satisfied the minimum quality criteria for approval. Seven excluded textbooks showed problems in all classes of evaluation criteria. All nine excluded textbooks exhibited problems related to conceptual correctness and adequacy, and accuracy of basic information. The most frequent qualities of approved textbooks concerned aspects of methodological adequacy and knowledge construction. We found no clear evidence that the frequency of choice of the approved textbooks by the high school teachers reflected the quality of the evaluated items, as established by the team which evaluated the textbooks

Comparative study of ochratoxin a exposure through the intake of cereal products in two climatic moroccan regions

The present study aims to compare ochratoxin A (OTA) exposure through the intake of three cereal derivative products (bread, pasta and semolina) in two different Moroccan climatic regions (littoral and continental). OTA weekly intakes from cereal products were calculated using a deterministic approach for each region. Results showed a statistically significant difference (p < 0.05) of OTA exposure between the two regions. Indeed, the median OTA exposure was estimated at 48.97 ng/kg b.w./week in the littoral region, while it was estimated at 6.36 ng/kg b.w./week in the continental region. The probabilistic approach showed that, due to uncertainties, the 95th percentile of weekly OTA exposure associated with the three cereal products ranged from 66.18 to 137.79 (95% CI) with a median of 97.44 ng/kg body weight (b.w.)/week. Compared to the threshold of 100 ng/kg b.w./week, 95% of the cumulative distributions predicted an exceedance frequency between 0.42 and 17.30% (95% CI), with an exceedance frequency median of 4.43%. Results showed that cereal derivatives constitute an important vector of OTA exposure and cause a significant exceedance of toxicological reference value among large consumers in the littoral region, which suggests the urgency of reconsidering the maximum regulatory limit (MRL) set for OTA (3 µg/kg) in cereal derivatives by Moroccan authorities.info:eu-repo/semantics/publishedVersio

Decomposing Noise in Biochemical Signaling Systems Highlights the Role of Protein Degradation

AbstractStochasticity is an essential aspect of biochemical processes at the cellular level. We now know that living cells take advantage of stochasticity in some cases and counteract stochastic effects in others. Here we propose a method that allows us to calculate contributions of individual reactions to the total variability of a system’s output. We demonstrate that reactions differ significantly in their relative impact on the total noise and we illustrate the importance of protein degradation on the overall variability for a range of molecular processes and signaling systems. With our flexible and generally applicable noise decomposition method, we are able to shed new, to our knowledge, light on the sources and propagation of noise in biochemical reaction networks; in particular, we are able to show how regulated protein degradation can be employed to reduce the noise in biochemical systems

The use of cosmic muons in detecting heterogeneities in large volumes

The muon intensity attenuation method to detect heterogeneities in large matter volumes is analyzed. Approximate analytical expressions to estimate the collection time and the signal to noise ratio, are proposed and validated by Monte Carlo simulations. Important parameters, including point spread function and coordinate reconstruction uncertainty are also estimated using Monte Carlo simulations.Comment: 8 pages, 11 figures, submetted to NIM

Phytochemical screening, nutritional value, antioxidant and antimicrobial activities and acute toxicity of Scolymus hispanicus: a wild edible plant in Morocco

Scolymus hispanicus L. (Golden thistle) is a well-known wild edible plant (WEP) in Morocco. However, the species value is not well investigated and its economic value is considerably low. Therefore, the aim of this work was to evaluate the phytochemical composition, the biological activities, and the acute toxicity of crude extract of S. hispanicus aerial parts. The mineral composition was assessed using an ICP-AES spectrometer and, the contents in polyphenol, flavonoids and tannins using colorimetric methods. The antioxidant activity was tested by DPPH assay. Disc diffusion and broth micro dilution methods were used to evaluate the antimicrobial activity. Moreover, the safety of the plant extract was validated by performing acute toxicity. The findings revealed that this plant is a rich source of protein, carbohydrates and minerals especially iron and, have high contents of polyphenols, flavonoids and tannins. The biological evaluation of the plant extracts exhibited a remarkable antioxidant content and, a wide antibacterial activity and yeast inhibition. The results indicated also that the tested extract is safe with an LD50 higher than 5000 mg.kg-1. The study data suggest that S. hispanicus could be a promising functional and nutraceutical food with antioxidant and antimicrobial potential and can contribute to a balanced diet.info:eu-repo/semantics/publishedVersio

Exploring the potential anti-inflammatory and wound-healing proprieties of Cepaea hortensis snail mucin

Long before its popularization as a skincare ingredient, snail slime was reported to have a variety of health-promoting attributes. Its medicinal use involved the treatment of ailments, such as anthrax, hernias, stomach pain, chest pain, as well as tuberculosis. The main aim of this study was to investigate the anti-inflammatory and wound-healing properties of snail slime from Cepaea hortensis (Müller, 1774) (brown garden snail). The slime was extracted by a mild method, and the anti-inflammatory characteristics were determined by croton-oil-induced mouse-ear edema. The histological study showed that the snail slime exerts its action at the level of inflammatory mediators, explaining the drastic decrease of edema (59% in comparison to the 47% of indomethacin). The daily application of 50 µL (15 mg/kg) of snail slime on excision wounds in rabbits proved to induce an almost full tissue repair after 24 days of treatment (87.80–92.7% wound closure in width and length, respectively). Analysis of the slime’s safety aspect allowed affirming the nontoxicity of snail slime on both the skin and eyes.info:eu-repo/semantics/publishedVersio

Desenvolvimento intrauterino da paca (cuniculus paca), um roedor histricomorfo precocial.

CNPq e CAPESO desenvolvimento intrauterino consiste em uma preparação dos recém-nascidos para a vida aérea. Além das relações filogenéticas, esta fase reflete as estratégias adotadas pelos mamíferos para maximizar a sobrevivência materna e neonatal, o que influencia fortemente na dinâmica de suas populações silvestres e na sua resiliência a distúrbios. Neste estudo, nós utilizamos amostras de 137 pacas (Cuniculus paca) gestantes, obtidas ao longo de 15 anos através de métodos colaborativos com caçadores locais na Amazônia, para descrever o desenvolvimento da morfologia externa e interna da espécie durante a fase intrauterina, discutindo a estratégia adotada pela espécie para sobrevivência do recém-nascido em comparação com outros roedores. Nos embriões/fetos adquiridos, foram realizados (i) a avaliação da probabilidade de presença de características externas ao longo da gestação; (ii) a biometria externa e uma estimativa da idade fetal e; (iii) medições do volume de órgãos torácicos e abdominais, comparando suas proporções com os órgãos de adultos. O comprimento fetal total (CRL) variou de 0,6 cm a 24,6 cm. As características fetais apareceram na seguinte ordem cronológica: membros, pálpebras, pálpebras fusionadas, genitália, orelha externa, pelagem tátil, garras, pele, pintas, pelagem de cobertura, dentes e pálpebras abertas. Fetos com CRL>19,5 cm apresentaram todas as características externas avaliadas. A fórmula de crescimento da idade fetal foi ∛W = 0,082 (t - 37,25), e a idade foi fortemente associada com CRL. O fígado mostrou uma tendência decrescente na sua proporção ao longo do desenvolvimento fetal, enquanto o volume relativo de órgãos gastrointestinais tubulares aumentou significativamente. Todos os órgãos, exceto o coração e o timo, apresentaram volumes relativos semelhantes entre fetos avançados e adultos. Este estudo revela que pacas produzem recém-nascidos precociais com estruturas adequadas para a sobrevivência com baixa dependência do cuidado parental. Além disso, os neonatos da espécie são mais desenvolvidos do que os de outros roedores estudados. Embora a paca seja atualmente a espécie mais caçada na Amazônia, sua estratégia reprodutiva não é compatível com uma condição de presa, sugerindo que a espécie não é reprodutivamente preparada para responder a altas pressões de caça. Portanto, nossos resultados têm uma importância crítica para o diagnóstico clínico e o manejo reprodutivo in situ e ex situ da espécie.The intrauterine development consists of a preparation of the neonates for the aerial life. Beyond the phylogenetic relationships, this phase reflects the strategies adopted by mammals to maximize the maternal and neonatal survival, which strongly influences the dynamics of their wild populations and their resilience to disturbances. Here, we used samples of 137 pregnant pacas (Cuniculus paca), obtained along 15 years through collaborative methods with local hunters in the Amazon, to describe the development of the external and internal morphology of the species during the intrauterine phase, discussing the newborn survival strategy adopted in comparison to other rodents. In the embryos/fetuses acquired, we performed (i) an assessment of the presence probability of external features along the gestation; (ii) an estimation of fetal age and an external biometry; and (iii) a measurement of the volume of thoracic and abdominal organs, comparing their relative volumes with those of adults. The crown-rump length (CRL) ranged from 0.6 cm to 24.6 cm. The fetal features appeared in the following chronological order: limbs, eyelid buds, fusioned eyelids, genitalia, outer ear, tactile pelage, claws, skin, skin spots, covering pelage, teeth and open eyelids. Fetuses with CRL > 19.5 cm presented all features assessed. The growth formula of fetal age was ∛W = 0.082 (t - 37.25), and the age was accurately associated with CRL. The liver showed a decreasing trend in its proportion in the internal cavity, while the relative volume of tubular gastrointestinal organs increased significantly. All organs but the heart and the thymus presented similar relative volumes between advanced fetuses and adults. This study reveals that pacas produce precocial neonates with appropriate structures for survival with low dependence on the mother’s care. In addition, the species’ neonates are more developed than other studied rodents. Although the paca is currently the most hunted species in the Amazon, its reproductive strategy is compatible to a low prey condition, suggesting that the species is not reproductively prepared to respond to high hunting pressures. Therefore, our results have a critical importance for clinical diagnosis and in situ and ex situ reproductive management of the species

The Density Profiles of Massive, Relaxed Galaxy Clusters. II. Separating Luminous and Dark Matter in Cluster Cores

We present stellar and dark matter (DM) density profiles for a sample of seven massive, relaxed galaxy clusters derived from strong and weak gravitational lensing and resolved stellar kinematic observations within the centrally-located brightest cluster galaxies (BCGs). In Paper I of the series, we demonstrated that the total density profile derived from these data, which span 3 decades in radius, is consistent with numerical DM-only simulations at radii >~ 5-10 kpc, despite the significant contribution of stellar material in the core. Here we decompose the inner mass profiles of these clusters into stellar and dark components. Parametrizing the DM density profile as a power law rho_DM ~ r^{-\beta} on small scales, we find a mean slope = 0.50 +- 0.10 (random) +0.14-0.13 (systematic). Alternatively, cored Navarro-Frenk-White (NFW) profiles with = 1.14 +- 0.13 (random) +0.14-0.22 (systematic) provide an equally good description. These density profiles are significantly shallower than canonical NFW models at radii <~ 30 kpc, comparable to the effective radii of the BCGs. The inner DM profile is correlated with the distribution of stars in the BCG, suggesting a connection between the inner halo and the assembly of stars in the central galaxy. The stellar mass-to-light ratio inferred from lensing and stellar dynamics is consistent with that inferred using stellar population synthesis models if a Salpeter initial mass function is adopted. We compare these results to theories describing the interaction between baryons and DM in cluster cores, including adiabatic contraction models and the possible effects of galaxy mergers and active galactic nucleus feedback, and evaluate possible signatures of alternative DM candidates.Comment: Updated to matched the published version in Ap