Suppression of two-bounce windows in kink-antikink collisions

We consider a class of topological defects in $(1,1)$-dimensions with a deformed $\phi^4$ kink structure whose stability analysis leads to a Schr\"odinger-like equation with a zero-mode and at least one vibrational (shape) mode. We are interested in the dynamics of kink-antikink collisions, focusing on the structure of two-bounce windows. For small deformation and for one or two vibrational modes, the observed two-bounce windows are explained by the standard mechanism of a resonant effect between the first vibrational and the translational modes. With the increasing of the deformation, the effect of the appearance of more than one vibrational mode is the gradual disappearance of the initial two-bounce windows. The total suppression of two-bounce windows even with the presence of a vibrational mode offers a counterexample from what expected from the standard mechanism. For even larger deformation, some two-bounce windows reappear, but with a non-standard structure.Comment: 13 pages, 6 figure

Estudo comparativo da atomização eletrotérmica de európio e disprósio em filamento de tungstênio e forno de grafite.

Os elementos lantanídeos são importantes para as indústrias óticas e eletrônica e como marcadores de digestibilidade animal. Esses elementos, dentre eles o európio e o disposto, formam carretos refratários quando submetidos a atomização eletrotécnica em atemorizadores de grafite, inclusive pirolíticos

Trigger synchronisation circuits in CMS

We present the principles of the CMS method for synchronizing the trigger data at LHC. The method makes use of the LHC bunch gap and allows for re-synchronisation of the data every LHC orbit. It relies on the distribution by the TTC system of a signal synchronous with the first bunch in the orbit, and is implemented by dedicated synchronisation circuits in each trigger link. We report on the test of a prototype FPGA implementation

Efeito de modificadores químicos sobre o comportamento eletrotérmico de selênio em digerido de material vegetal.

A demanda crescente por alimentação balanceada tem despertado interesse em dietas diferenciadas baseadas em alimentos funcionais, os quais possuem propriedades ou substancias bioativas capazes de modular alguma função no organismo. As crucíferas, vegetais com capacidade de absorver altos teores de Se, compõem um grupo de uma série de alimentos desse tipo. A determinação de Se nesses vegetais é de interesse em função tanto de sua importância no metabolismo humano e animal como do ponto de vista de sua toxicidade. Com relação a determinação de Se por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite (GFAAS), os modificadores químicos convencionais mais citados são: Pd(NO3)2, Mg(NO3)2, Ni(NO3)2, Pd(NO3)2 + Mg(NO3)2,- Pd(NO3)2 + Cd(NO3)2, Pd(NO3)2+ acido ascórbico; Pd (pré-reduzido). Neste trabalho foi avaliada a influência de modificadores químicos sobre o comportamento eletrotérmico de Se em um vegetal da classe das cruciferas (nabo) empregando curvas de pirólise e atomização em presença de Pd(II), Ni(II), Mg(II), Pd pré-reduzido e das misturas Pd(II)/Mg(II) e Pd(II)/Cd(II). Foram preparadas soluções analíticas contendo 20 pg Se L-1 em meio 0,014 mol L-1 HNO3 e 30 pg Se L -1 em digerido do material vegetal

Screening of perfused combinatorial 3D microenvironments for cell culture

Biomaterials combining biochemical and biophysical cues to establish close-to-extracellular matrix (ECM) models have been explored for cell expansion and differentiation purposes. Multivariate arrays are used as material-saving and rapid-to-analyze platforms, which enable selecting hit-spotted formulations targeting specific cellular responses. However, these systems often lack the ability to emulate dynamic mechanical aspects that occur in specific biological milieus and affect physiological phenomena including stem cells differentiation, tumor progression, or matrix modulation. We report a tailor-made strategy to address the combined effect of flow and biochemical composition of three-dimensional (3D) biomaterials on cellular response. We suggest a simple-to-implement device comprising (i) a perforated platform accommodating miniaturized 3D biomaterials and (ii) a bioreactor that enables the incorporation of the biomaterial-containing array into a disposable perfusion chamber. The system was upscaled to parallelizable setups, increasing the number of analyzed platforms per independent experiment. As a proof-of-concept, porous chitosan scaffolds with 1 mm diameter were functionalized with combinations of 5 ECM and cell-cell contact-mediating proteins, relevant for bone and dental regeneration, corresponding to 32 protein combinatorial formulations. Mesenchymal stem cells adhesion and production of an early osteogenic marker were assessed on-chip on static and under-flow dynamic perfusion conditions. Different hit-spotted biomaterial formulations were detected for the different flow regimes using direct image analysis. Cell-binding proteins still poorly explored as biomaterials components amelogenin and E-cadherin - were here shown as relevant cell response modulators. Their combination with ECM cell-binding proteins - fibronectin, vitronectin, and type 1 collagen - rendered specific biomaterial combinations with high cell adhesion and ALP production under flow. The developed versatile system may be targeted at wM.B. Oliveira acknowledges the financial support from Portuguese Foundation for Science and Technology- FCT (Grant SFRH/BPD/111354/2015). This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013) and IPC/i3N Minho (FCT Ref. UID/CTM/50025/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. This work was also supported by European Research Council grant agreement ERC-2014-ADG-669858 (project ATLAS)

Intermittent reconnection and plasmoids in UV bursts in the low solar atmosphere

Magnetic reconnection is thought to drive a wide variety of dynamic phenomena in the solar atmosphere. Yet the detailed physical mechanisms driving reconnection are difficult to discern in the remote sensing observations that are used to study the solar atmosphere. In this paper we exploit the high-resolution instruments Interface Region Imaging Spectrograph (IRIS) and the new CHROMIS Fabry-Perot instrument at the Swedish 1-m Solar Telescope (SST) to identify the intermittency of magnetic reconnection and its association with the formation of plasmoids in so-called UV bursts in the low solar atmosphere. The Si IV 1403A UV burst spectra from the transition region show evidence of highly broadened line profiles with often non-Gaussian and triangular shapes, in addition to signatures of bidirectional flows. Such profiles had previously been linked, in idealized numerical simulations, to magnetic reconnection driven by the plasmoid instability. Simultaneous CHROMIS images in the chromospheric Ca II K 3934A line now provide compelling evidence for the presence of plasmoids, by revealing highly dynamic and rapidly moving brightenings that are smaller than 0.2 arcsec and that evolve on timescales of order seconds. Our interpretation of the observations is supported by detailed comparisons with synthetic observables from advanced numerical simulations of magnetic reconnection and associated plasmoids in the chromosphere. Our results highlight how subarcsecond imaging spectroscopy sensitive to a wide range of temperatures combined with advanced numerical simulations that are realistic enough to compare with observations can directly reveal the small-scale physical processes that drive the wide range of phenomena in the solar atmosphere.Comment: Accepted for publication in Astrophysical Journal Letters. Movies are available at http://folk.uio.no/rouppe/plasmoids_chromis

Open vessel microwave extraction of metals in biological and botanical materials.

The complete sample decomposition is not always necessary when measurements are carried out using optical techniques. Depending on both technique employed and sample matrix characteristics, an extraction procedure can be completely suitable for quantitative determinations. To implement this approach is essential to perform a critical evaluation of the behavior of each element, of the extractor solution, and of the temperature and time of extraction. The temperature can be controlled adopting microwave-assisted procedures that guarantee fast heating and repeatability. In this work an open-vessel microwave system (Star 6, CEM) was employed to investigate the efficiency of the extraction procedures. The extraction of Al, Ca, Cu, Fe, Mg, Mn,:and Zn was evaluated in biological (bovine liver, SRM 1577b, NIST) and botanical (apple leaves, SRM 1515, NIST; trace elements in spinach leaves, SR!vf 1570a, NIST; and commercial teas) materials. The extraction procedures were investigated using 1 or 10% v/v hydrochloric or nitric acid solutions. An alkaline solution containing a mixture of water- soluble tertiary amines (CFA-C, Spectrasol) was also tested. All procedures were carried out at temperatures in the range 80-105 oC during time intervals shorter than 10 min. The analytes were determined by flame and graphite furnace atomic absorption spectrophotometry (Intralab, model Gemini AA12/1475 and Varian model 800, respectively), and by inductively coupled plasma atomic emission spectrometry (AtomScan 25, TJA). Copper, Mn, and Zn were quantitatively extracted from biological and botanical materials with all solutions employed. The complete extraction of these elements from biological materials was easier than from botanical materials and it was also observed that acid solutions were more efficient than the CFA-C mixture for botanical samples. Calcium and Mg were quantitatively extracted in some tea samples and it was found that Mg is weaker bound to the matrix than Ca. Aluminum and Fe were poorly extracted in all samples