The effect of a stellar magnetic variation on the jet velocity

Stellar jets are normally constituted by chains of knots with some periodicity in their spatial distribution, corresponding to a variability of order of several years in the ejection from the protostar/disk system. A widely accepted theory for the presence of knots is related to the generation of internal working surfaces due to variations in the jet ejection velocity. In this paper we study the effect of variations in the inner disk-wind radius on the jet ejection velocity. We show that a small variation in the inner disk-wind radius produce a variation in the jet velocity large enough to generate the observed knots. We also show that the variation in the inner radius may be related to a variation of the stellar magnetic field.Comment: 5 pages, 3 figures, accepted for publication in Ap

Synthesis, structure, and optical properties of an alternating calix[4]arene-based meta-linked phenylene ethynylene copolymer

Novel alternating copolymers comprising biscalix[4]arene-p-phenylene ethynylene and m-phenylene ethynylene units (CALIX-m-PPE) were synthesized using the Sonogashira-Hagihara cross-coupling polymerization. Good isolated yields (60-80%) were achieved for the polymers that show M-n ranging from 1.4 x 10(4) to 5.1 x 10(4) gmol(-1) (gel permeation chromatography analysis), depending on specific polymerization conditions. The structural analysis of CALIX-m-PPE was performed by H-1, C-13, C-13-H-1 heteronuclear single quantum correlation (HSQC), C-13-H-1 heteronuclear multiple bond correlation (HMBC), correlation spectroscopy (COSY), and nuclear overhauser effect spectroscopy (NOESY) in addition to Fourier transform-Infrared spectroscopy and microanalysis allowing its full characterization. Depending on the reaction setup, variable amounts (16-45%) of diyne units were found in polymers although their photophysical properties are essentially the same. It is demonstrated that CALIX-m-PPE does not form ground-or excited-state interchain interactions owing to the highly crowded environment of the main-chain imparted by both calix[4]arene side units which behave as insulators inhibiting main-chain pi-pi staking. It was also found that the luminescent properties of CALIX-m-PPE are markedly different from those of an all-p-linked phenylene ethynylene copolymer (CALIX-p-PPE) previously reported. The unexpected appearance of a low-energy emission band at 426 nm, in addition to the locally excited-state emission (365 nm), together with a quite low fluorescence quantum yield (Phi = 0.02) and a double-exponential decay dynamics led to the formulation of an intramolecular exciplex as the new emissive species

Solid-state sensory properties of Calix-Poly(Phenylene Ethynylene)s toward nitroaromatic explosives

This study is primarily focused in establishing the solid-state sensory abilities of several luminescent polymeric calix[4]arene-based materials toward selected nitroaromatic compounds (NACs), creating the foundations for their future application as high performance materials for detection of high explosives. The phenylene ethynylene-type polymers possessing bis-calix[4]arene scaffolds in their core were designed to take advantage of the known recognition abilities of calixarene compounds toward neutral guests, particularly in solid-state, therefore providing enhanced sensitivity and selectivity in the sensing of a given analyte. It was found that all the calix[4]arene-poly(para-phenylene ethynylene)s here reported displayed high sensitivities toward the detection of nitrobenzene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene (TNT). Particularly effective and significant was the response of the films (25-60 nm of thickness) upon exposure to TNT vapor (10 ppb): over 50% of fluorescence quenching was achieved in only 10 s. In contrast, a model polymer lacking the calixarene units showed only reduced quenching activity for the same set of analytes, clearly highlighting the relevance of the macrocyclics in promoting the signaling of the transduction event. The films exhibited high photostability (less than 0.5% loss of fluorescence intensity up to 15 min of continuous irradiation) and the fluorescence quenching sensitivity could be fully recovered after exposure of the quenched films to saturated vapors of hydrazine (the initial fluorescence intensities were usually recovered within 2-5 min of exposure to hydrazine)

Photon bubble turbulence in cold atom gases

Turbulent radiation flow is commonplace in systems with strong, incoherent, light-matter interactions. In astrophysical contexts, photon bubble turbulence is considered a key mechanism behind enhanced radiation transport, and its importance has been widely asserted for a variety of high energy objects such as accretion disks and massive stars. Here, we show that analogous conditions to those of dense astrophysical objects can be obtained in large clouds of cold atoms, prepared in a laser-cooling experiment, driven close to a sharp electronic resonance. By accessing the spatially-resolved atom density, we are able to identify a photon bubble instability and the resulting regime of photon bubble turbulence. We also develop a theoretical model describing the coupled dynamics of both photon and atom gases, which accurately describes the statistical properties of the turbulent regime. This study thus opens the possibility of simulating radiation-dominated astrophysical systems in cold atom experiments.European Union's Horizon 2020 Research and Innovation programme 820392; Portuguese Foundation for Science and Technology PD/BD/135211/2017info:eu-repo/semantics/publishedVersio

Quasi-static and dynamic photon bubbles in cold atom clouds

Turbulent radiation flow is ubiquitous in many physical systems where light–matter interaction becomes relevant. Photon bubble instabilities, in particular, have been identified as a possible source of turbulent radiation transport in astrophysical objects such as massive stars and black hole accretion disks. Here, we report on the experimental observation of a photon bubble instability in cold atomic gases, in the presence of multiple scattering of light. Two different regimes are identified, namely, the growth and formation of quasi-static structures of depleted atom density and increased photon number, akin to photon bubbles in astrophysical objects, and the destabilisation of these structures in a second regime of photon bubble turbulence. A two-fluid theory is developed to model the coupled atom–photon gas and to describe both the saturation of the instability in the regime of quasi-static bubbles and the low-frequency turbulent phase associated with the growth and collapse of photon bubbles inside the atomic sample. We also employ statistical dimensionality reduction techniques to describe the low-dimensional nature of the turbulent regime. The experimental results reported here, along with the theoretical model we have developed, may shed light on analogue photon bubble instabilities in astrophysical scenarios. Our findings are consistent with recent analyses based on spatially resolved pump–probe measurements.info:eu-repo/semantics/publishedVersio

Design e validação de um modelo de reabilitação com implantes curtos

Objectives: This research intended to develop and validate a digital model that could be used to study the stresses and strains created in the different components involved in oral fixed rehabilitations with short implants. The validated model was then used to simulate a clinical- like situation. Methods: A digital model was created considering the posterior areas of the mandible. Its materialization obtained ten specimens of the experimental prototype. Seven of them were static compressive tested until failure and, for the other three, the tests were progressively interrupted, to allow the establishment of a damage sequence. On the numerical model a finite element analysis was performed with Abaqus software, under similar conditions to the experimental situation. Results: The stress pattern on the FEA and the failure location on the static test were similar. The sequence in which each part reached the yield strength was the same as that observed on the interrupted static test (resin, prosthetic framework, implants and implant screws, in this order). Due to these results, the model was considered valid. A clinical-like simulation with the validated model showed that buccal cortical bone, around the implants platform, is the weakest part of such a rehabilitation. Conclusions: This research allowed the development and validation of a computer-aided design model that can be used to study an oral fixed rehabilitation supported by short implants. For clinical purposes, it is important to refer that the highest stress and strain values were found on the cortical bone around the buccal aspect of the implants.Objetivos: O objetivo desta investigação foi o desenvolvimento e validação experimental de um modelo digital, que permita o estudo das tensões e deformações geradas nos diferentes componentes de uma reabilitação oral fixa sobre implantes curtos. O modelo obtido foi então usado para simular uma situação clinica. Métodos: Um modelo numérico foi criado considerando a região posterior da mandibula. A sua materialização permitiu obter dez amostras do protótipo experimental. Sete delas foram sujeitas a ensaios estáticos de compressão até à falência. Nas restantes três, os ensaios foram interrompidos com forças gradualmente crescentes, estabelecendo a sequência pela qual os componentes se deformaram. O modelo numérico foi também sujeito a uma simulação com elementos finitos, usando o software Abaqus, em condições semelhantes à simulação experimental. Resultados: O padrão de tensões obtido no modelo numérico foi similar à localização das fraturas no modelo experimental. A sequência segundo a qual a tensão de cedência foi alcançada em cada parte do modelo numérico foi a mesma encontrada quando o ensaio estático se interrompeu (por esta ordem: resina, prótese, implantes e parafusos). Estes resultados permitiram considerar o modelo válido. A simulação de uma situação clínica, com o modelo validado, revelou que o osso cortical, em vestibular da plataforma dos implantes, é a região mais débil da reabilitação. Conclusões: Esta investigação permitiu o desenvolvimento e a validação de um modelo que permite o estudo de reabilitações fixas sobre implantes curtos. Clinicamente é importante realçar que o osso cortical é a zona que apresenta tensões e deformações mais elevadas. (Rev Port Estomatol Med Dent Cir Maxilofac. 2017;58(2):79-90)info:eu-repo/semantics/publishedVersio

Colonization of rice and Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) larvae by genetically modified endophytic Methylobacterium mesophilicum

The colonization of Spodoptera frugiperda J.E. Smith larvae and rice seedlings by genetically modified endophytic bacterium Methylobacterium mesophilicum, and also the possible transfer of this bacterium to inside the larva's body during seedlings consumption were studied. The data obtained by bacterial reisolation and fluorescence microscopy showed that the bacterium colonized the rice seedlings, the larva's body and that the endophytic bacteria present in seedlings could be acquired by the larvae. In that way, the transference of endophytic bacterium from plants to insect can be a new and important strategy to insect control using engineered microorganisms.CNPq National Council of Researc