DFTB+, a software package for efficient approximate density functional theory based atomistic simulations.

DFTB+ is a versatile community developed open source software package offering fast and efficient methods for carrying out atomistic quantum mechanical simulations. By implementing various methods approximating density functional theory (DFT), such as the density functional based tight binding (DFTB) and the extended tight binding method, it enables simulations of large systems and long timescales with reasonable accuracy while being considerably faster for typical simulations than the respective ab initio methods. Based on the DFTB framework, it additionally offers approximated versions of various DFT extensions including hybrid functionals, time dependent formalism for treating excited systems, electron transport using non-equilibrium Green's functions, and many more. DFTB+ can be used as a user-friendly standalone application in addition to being embedded into other software packages as a library or acting as a calculation-server accessed by socket communication. We give an overview of the recently developed capabilities of the DFTB+ code, demonstrating with a few use case examples, discuss the strengths and weaknesses of the various features, and also discuss on-going developments and possible future perspectives.

Atitudes em relação à Bioestatística de discentes e docentes da Faculdade de Ciências Farmacêuticas de Araraquara-UNESP / Attitudes towards Biostatistics of students and teachers at the Faculty of Pharmaceutical Sciences of Araraquara-UNESP

O objetivo deste estudo foi verificar a atitude de discentes e docentes da Faculdade de Ciências Farmacêuticas de Araraquara (UNESP) em relação à Bioestatística. Como instrumento de medida, utilizou-se a Escala de Atitudes em Relação à Estatística (EAE). A reprodutibilidade da Escala foi estimada pela estatística Kappa (κ) com ponderação linear e sua consistência interna pelo Coeficiente alfa-Cronbach (α). Os indivíduos foram agrupados segundo sua atitude em relação à Estatística em positiva e negativa; posteriormente, estudou-se sua associação com as variáveis de interesse pelo teste de quiquadrado (x2) ao nível de significância de 5%. A amostra foi composta por 272 alunos de graduação, 83 de pósgraduação e 24 docentes, sendo predominantemente feminina (78,2%). Entre os estudantes, 67,5% participaram do programa de iniciação científica. A reprodutibilidade e a consistência interna da Escala foram adequadas (κ=0,7093; α=0,9334). A maior parte da amostra (74,4%) apresentou atitude positiva frente à Estatística. Houve associação entre a atitude e a atividade funcional (p=0,0204), série cursada (p=0,0316) e desempenho (p=0,0002). Assim, concluise que a maioria dos participantes apresentou atitude positiva em relação à Bioestatística, sendo que os estudantes de graduação e aqueles que relataram bom desempenho em Bioestatística apresentaram proporção significativamente maior de atitude positiva em relação aos demais.

In this study, the attitudes of students and teachers at the Faculty of Pharmaceutical Sciences of Araraquara (UNESP University) towards Biostatistics were assessed. The Survey of Attitudes Toward Statistics (SATS) scale was used as the measuring instrument. The reproducibility of the scale was estimated by Cohen's Kappa (k) coefficient with linear weighting and its internal consistency by Cronbach's alpha coefficient (α). The individuals were first placed in two groups, according to their positive or negative attitude toward Statistics; then, the association of their attitude with the variables of interest was tested by the chi-squared (χ2) test at a significance level of 5%. The sample consisted of 272 undergraduate students, 83 graduate students and 24 teachers, predominantly female (78.2%). Among the students, 67.5% participated in the scientific research initial training program. Reproducibility and internal consistency of the scale were adequate ((κ=0.7093; α=0.9334). Most of the subjects (74.4%) had a positive attitude toward Statistics. Significant association was found between attitude and functional activity (p=0.0204), the course taken (p=0.0316) and effort (p=0.0002). Thus, it was concluded that the great majority of the participants had a positiveattitude towards Biostatistics and that undergraduate students and those who reported good performance in Biostatistics showed a significantly higher proportion of positive attitude than the other students.

Mesenchymal stem cell interaction with a non-woven hyaluronan-based scaffold suitable for tissue repair.

The fabrication of biodegradable 3-D scaffolds enriched with multipotent stem cells seems to be a promising strategy for the repair of irreversibly injured tissues. The fine mechanisms of the interaction of rat mesenchymal stem cells (rMSCs) with a hyaluronan-based scaffold, i.e. HYAFF(R)11, were investigated to evaluate the potential clinical application of this kind of engineered construct. rMSCs were seeded (2 x 10(6) cells cm(-2)) on the scaffold, cultured up to 21 days and analysed using appropriate techniques. Light (LM), scanning (SEM) and transmission (TEM) electron microscopy of untreated scaffold samples showed that scaffolds have a highly porous structure and are composed of 15-microm-thick microfibres having a rough surface. As detected by trypan blue stain, cell adhesion was high at day 1. rMSCs were viable up to 14 days as shown by CFDA assay and proliferated steadily on the scaffold as revealed by MTT assay. LM showed rMSCs in the innermost portions of the scaffold at day 3. SEM revealed a subconfluent cell monolayer covering 40 +/- 10% of the scaffold surface at day 21. TEM of early culture showed rMSCs wrapping individual fibres with regularly spaced focal contacts, whereas confocal microscopy showed polarized expression of CD44 hyaluronan receptor; TEM of 14-day cultures evidenced fibronexus formation. Immunohistochemistry of 21-day cultures showed that fibronectin was the main matrix protein secreted in the extracellular space; decorin and versican were seen in the cell cytoplasm only and type IV collagen was minimally expressed. The expression of CD90, a marker of mesenchymal stemness, was found unaffected at the end of cell culture. Our results show that HYAFF(R)11 scaffolds support the adhesion, migration and proliferation of rMSCs, as well as the synthesis and delivery of extracellular matrix components under static culture conditions without any chemical induction. The high retention rate and viability of the seeded cells as well as their fine modality of interaction with the substrate suggest that such scaffolds could be potentially useful when wide tissue defects are to be repaired as in the case of cartilage repair, wound healing and large vessel replacement.