Effect of noise in open chaotic billiards

We investigate the effect of white-noise perturbations on chaotic trajectories in open billiards. We focus on the temporal decay of the survival probability for generic mixed-phase-space billiards. The survival probability has a total of five different decay regimes that prevail for different intermediate times. We combine new calculations and recent results on noise perturbed Hamiltonian systems to characterize the origin of these regimes, and to compute how the parameters scale with noise intensity and billiard openness. Numerical simulations in the annular billiard support and illustrate our results.Comment: To appear in "Chaos" special issue: "Statistical Mechanics and Billiard-Type Dynamical Systems"; 9 pages, 5 figure

Characterization of Biocompatible Poly(Ethylene Glycol)-Dimethacrylate Hydrogels for Tissue Engineering

Acknowledgements: This work is supported by the Fundação para a Ciência e a Tecnologia (FCT) and Centro2020 through the Project references: UID/Multi/04044/2013 and PAMI - ROTEIRO/0328/2013 (Nº022158). It is also funded by the projects insitu.Biomas (POCI-01-0247-FEDER-017771), and NEXT. parts (POCI-01-0247-FEDER-017963) from the Portuguese National Innovation Agency.Tissue Engineering depends on broadly techniques to regenerate tissues and/or organ functions. To do so, tailored polymeric and/or hydrogel scaffolds may be used to ensure the appropriate regeneration. Hydrogels are suitable materials for constructing cell-laden matrices as they can be produced with incorporation of cells and rapidly cross-linked in situ through photopolymerisation reactions. Measurement of the polymerization degree, as well as resistance to compression and water retention are fundamental tests to evaluate the characteristics of hydrogels. In this work, free-radical polymerisation of poly(ethylene glycol)-dimethacrylate (PEGDMA) in UV light was assessed. Several hydrogels with different photoinitiator and water contents were produced to evaluate their influence on hydrogels behaviour. Experiments showed that variations on water and photoinitiator content induce changes in the physical and chemical behaviour of hydrogels. As it was found, water content prevents polymerisation to occur and reduces the mechanical properties of hydrogels weakening them. Furthermore, differences were found in varying water content from 15 to 30%, since this increase turned hydrogels more fragile and increase their stabilization time for water retention.info:eu-repo/semantics/publishedVersio

From Bloch Oscillations to a Steady-State Current in Strongly Biased Mesoscopic Devices

It has long been known that quantum particles in a periodic lattice exhibit an oscillatory motion that is solely driven by a constant and uniform force field. In a strongly biased mesoscopic device, this would appear as an ongoing time-dependent current oscillation (a Bloch oscillation) but, even when electrons can move coherently and without scattering, a steady-state regime of charge transport (a Landauer current) have been seen to quickly emerge. Here, we theoretically investigate the non-equilibrium current dynamics of a strongly biased two-terminal mesoscopic device, in order to show that such a system can exhibit Bloch oscillations as a transient regime that relaxes into a Landauer steady-state from charge being drained into the leads. Analytical results from the one-dimensional Wannier-Stark ladder problem are combined with numerical quantum time-evolution of a tight-binding toy model with finite leads to characterize the decay times of transient Bloch oscillations and establish the conditions under which they can occur.Comment: Preliminary Version (13 pages + 12 Figures). Comments and Suggestions are Welcome

Preliminary Assays towards Melanoma Cells Using Phototherapy with Gold-Based Nanomaterials

Supplementary Materials - The following are available online at https://www.mdpi.com/2079-4991/10/8/1536/s1, Video S1: Thermal activation of HAOA-coated GNPs.Cancer like melanoma is a complex disease, for which standard therapies have significant adverse side effects that in most cases are ineffective and highly unspecific. Thus, a new paradigm has come with the need of achieving alternative (less invasive) and effective therapies. In this work, biocompatible gold nanoparticles (GNPs) coated with hyaluronic acid and oleic acid were prepared and characterized in terms of size, morphology and cytotoxicity in the presence of Saccharomyces cerevisiae, and two cell lines, the keratinocytes (healthy skin cells, HaCat) and the melanoma cells (B16F10). Results showed that these GNPs absorb within the near-infrared region (750–1400 nm), in the optical therapeutic window (from 650 to 1300 nm), in contrast to other commercial gold nanoparticles, which enables light to penetrate into deep skin layers. A laser emitting in this region was applied and its effect also analyzed. The coated GNPs showed a spherical morphology with a mean size of 297 nm without cytotoxic effects towards yeast and tested cell lines. Nevertheless, after laser irradiation, a reduction of 20% in B16F10 cell line viability was observed. In summary, this work appears to be a promising strategy for the treatment of non-metastatic melanoma or other superficial tumors.This research was funded by Fundação para a Ciência e a Tecnologia (FCT) through the projects: UIDB/00645/2020, UID/DTP/04138/2019, PTDC/MED-QUI/31721/2017 as well as by the PhD fellowship SFRH/BD/148044/2019 (J.L.).info:eu-repo/semantics/publishedVersio

Preliminary assays towards melanoma cells using phototherapy with gold-based nanomaterials

UIDB/00645/2020 UID/DTP/04138/2019 PTDC/MED-QUI/31721/2017 SFRH/BD/148044/2019Cancer like melanoma is a complex disease, for which standard therapies have significant adverse side effects that in most cases are ineffective and highly unspecific. Thus, a new paradigm has come with the need of achieving alternative (less invasive) and effective therapies. In this work, biocompatible gold nanoparticles (GNPs) coated with hyaluronic acid and oleic acid were prepared and characterized in terms of size, morphology and cytotoxicity in the presence of Saccharomyces cerevisiae, and two cell lines, the keratinocytes (healthy skin cells, HaCat) and the melanoma cells (B16F10). Results showed that these GNPs absorb within the near-infrared region (750–1400 nm), in the optical therapeutic window (from 650 to 1300 nm), in contrast to other commercial gold nanoparticles, which enables light to penetrate into deep skin layers. A laser emitting in this region was applied and its effect also analyzed. The coated GNPs showed a spherical morphology with a mean size of 297 nm without cytotoxic effects towards yeast and tested cell lines. Nevertheless, after laser irradiation, a reduction of 20% in B16F10 cell line viability was observed. In summary, this work appears to be a promising strategy for the treatment of non-metastatic melanoma or other superficial tumors.publishersversionpublishe

Cadeia produtiva da piscicultura no estado do Maranhão

A piscicultura é uma solução para várias problemáticas. A prática de produção de peixes como um complemento para o abastecimento de alimento para as pessoas está sendo utilizada há centenas de anos com o seu desenvolvimento gradativo. Do ponto de vista dos procedimentos técnicos adotados, pode-se classificar a pesquisa como bibliográfica documental com o levantamento de dados em fontes primárias e secundárias. A pesquisa teve como objetivo apresentar as pisciculturas do Estado do Maranhão, e gerar informações que possam servir de subsídio para implementação de ações. Coletou-se os dados na Agência Estadual de Pesquisa Agropecuária e Extensão Rural do Maranhão (AGERP) e Agência Estadual de Defesa Agropecuária do Maranhão (AGED). Dentre as espécies cultivadas no estado do Maranhão, oito são espécies nativas, como tambaqui, pirarucu, piraíba, pirarara, pacu, dourado, surubim e tucunaré. A espécie que se destacou na produção foi o Tambaqui Colossomamacropomum. De acordo com os resultados da pesquisa. Em relação as cidades que exportam peixes do Maranhão, 32% do efetivo é originário de Senador La Rocque. Quanto a finalidade do peixe, 1%, são destinados para o abate, 18% são destinados a feiras locais e atravessadores que vendem peixes de porta em porta, 81% dos peixes são enviados para outros estados para cria e engorda. Com isso mantendo a diversidade socioambiental das cidades produtoras de peixe do Maranhão.A piscicultura é uma solução para o problema da falta de recursos naturais e de alimentos. A prática da piscicultura como complemento do abastecimento alimentar às pessoas tem sido aplicada há anos com o seu desenvolvimento gradual e pela necessidade básica de alimentação. Faça ponto de vista dos procedimentos técnicos adotados, é possível classificar uma pesquisa como uma bibliografia documental com coleta de dados em fontes primárias e secundárias. Os dados foram coletados na Agência Estadual de Pesquisa e Extensão Agropecuária do Maranhão (AGERP) e Agência Estadual de Defesa Agropecuária do Maranhão (AGED). Entre as espécies cultivadas no estado do Maranhão, oito são espécies nativas, como tambaqui, pirarucu, piraíba, pirarara, pacu, dourado, surubim e tucunaré.A espécie que mais se destacou na produção foi o Tambaqui Colossoma macropomum . De acordo com os resultados da pesquisa, 71% dos peixes enviados para outros estados abastecem o Pará. Em relação às cidades que exportam pescado do Maranhão, 32% da população é de Senador La Rocque. Isso garante o desejo da comunidade em atender ao manejo dos recursos naturais e, consequentemente, à reprodução cultural, mantendo uma diversidade socioambiental dos municípios maranhenses dos produtores de peixes.

Influence of voxel size on the accuracy of linear measurements of the condyle in images of cone beam computed tomography : a pilot study

To analyze the influence of voxel size and exposure time on the accuracy of linear measurements of the condyle. Four macerated hemi-mandibles of pigs were scanned in nine different voxel size protocols. Three-dimensional models of the condyle were generated in order to establish a comparison between linear measurements obtained with each voxel protocol and those obtained with a caliper (gold standard). The comparison between the protocols was performed considering the average of the two measurements of the condyle in the latero-medial (LM) and antero-posterior (AP) axes and also through repeated measurement ANOVA with rank transformation. The level of significance was 5%. A significant difference was found between the protocols regarding the LM and AP variables (p-values = 0.0027 and 0.0263, respectively). In the LM axis, the protocol P6 (voxel size of 0.3 mm with scan time of 4.8 seconds) did not show statistical difference compared to the gold standard. The protocols P4 and P5 (voxel size of 0.25 mm with scan times of 14.7 and 26.9 seconds, respectively) were both statistically similar compared to caliper, although they have presented a longer scan time. In the AP axis, the protocol P8 (voxel size of 0.4 mm with time scan of 4.8 seconds) was statistically similar to the gold standard. A smaller voxel size does not necessarily mean more accuracy regarding the linear measurements of the condyle. It is possible to obtain an acceptable level of accuracy with a larger voxel size and a shorter exposure time to radiation