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991.
The need for purely laboratory-based light pseudoscalar particles searches has been emphasized many times in the literature, since astrophysical bounds on these particles rely on several assumptions to calculate the flux produced in stellar plasmas. In this Letter we study the use of light from synchrotron accelerators as a source for a photon regeneration experiment also know as “light shining through a wall”. Such an experiment can significantly improve present limits on the pseudoscalar particle mass and the pseudoscalar–photon coupling constant obtained from laser experiments. This is possible even using a small number of powerful magnets (B∼10 T), due to the large incident photon flux. On the other hand, the use of a broadband incident photon-beam instead of infrared or optical lasers allows a significant improvement in the mass reach of the experiment (it is possible to test masses up to 0.01 eV without a drop in sensitivity). Large, but still feasible, configurations can explore in a quite model-independent way a large part of the parameter space examined by solar searches and HB stars in globular clusters. Additionally, the proposal may be useful for testing string motivated effective theories containing light and weakly interacting particles. 相似文献
992.
Heloisa R. Cadorim Mauana Schneider Júlia Hinz Fabiana Luvizon Adriana N. Dias 《Analytical letters》2019,52(13):2133-2149
A new procedure for the preconcentration of trace amounts of free Pb and Cd by disposable pipette extraction (DPX) is proposed herein. Recycled cork is used as a biosorbent and the procedure is completely free of organic solvents. The cork was reduced to a powder and characterized by scanning electron microscopy. Several parameters that influence the preconcentration of Pb and Cd with DPX-cork, such as the sample pH, number of extraction cycles, biosorbent mass, and percentage of acid in the desorption step, were studied. The tolerance of DPX-cork with respect to 10 potential interfering ions was also evaluated. Coupled with the high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) technique, the sample preparation method allowed the analytical limits required for quality control (according to the permitted limits established by legislation) to be obtained. The limits of detection for the extraction of a 3.5-mL water sample were 200?ng L?1 for Pb and 100?ng L?1 for Cd. The relative standard deviations were around 7.5% for Pb and 8.0% for Cd. The optimized method was successfully applied to the determination of Cd and Pb in two certified reference materials (water and wastewater) and five water samples (collected from a mangrove, a creek, and the sea). 相似文献
993.
Sustainability, eco‐efficiency, pollution prevention, industrial ecology, and green chemistry are considering platform‐based approaches to the development of the next generation of products and processes. Recently, renewable alternatives to traditional petroleum‐derived plastics have motivated recent interest in bio‐based composite materials which can contribute to the reduction of the environmental footprint. Lignin is a complex and amorphous biopolymer with a high density of functional groups and high modulus, which makes it potentially promising for material applications. In this sense, lignin can potentially be employed to improve the performance of materials and an economical alternative to convert lignin into high value‐added materials. Two different types of Kraft lignin were incorporated into polypropylene to fabricate composites with high bio‐content. In this study, polypropylene, Kraft lignin, and coupling agent were subjected to reactive extrusion. The composites prepared by melt processing were compared in terms of morphological, mechanical, and thermal characterizations. The results revealed that the incorporation of lignin into polypropylene matrix resulted in composites with properties suitable for various industrial sectors, especially those in which mechanical and thermal properties are crucial, such as the replacement of engineering plastics and polypropylene mineral filled. As a result, this work provides an effective way of using lignin as a low‐cost bio‐renewable resource in the plastics industry. 相似文献
994.
Alline L. B. Dias Hellen R. F. Batista Elisângela B. B. Estevam Cassia C. F. Alves Moacir R. Forim Heloiza D. Nicolella 《Natural product research》2019,33(17):2566-2570
In this study, the chemical composition and antibacterial and antiproliferative potential of the essential oil obtained from fresh leaves of Psidium myrtoides (PM-EO) against oral pathogens and human tumour cell lines were investigated for the first time. GC-FID and GC-MS analyses showed that trans-β-caryophyllene (30.9%), α-humulene (15.9%), α-copaene (7.8%), caryophyllene oxide (7.3%) and α-bisabolol (5.3%) are the major constituents of PM-EO. The antibacterial activity of PM-EO against a panel of oral pathogens was investigated in terms of their minimal inhibitory concentrations (MIC) using the broth microdilution method. PM-EO displayed moderate activity against Streptococcus mitis (MIC = 100 μg/mL), S. sanguinis (MIC = 100 μg/mL), S. sobrinus (MIC = 250 μg/mL), and S. salivarius (MIC = 250 μg/mL), and strong activity against S. mutans (MIC = 62.5 μg/mL). The antiproliferative activity in normal (GM07492A, lung fibroblasts) and tumour cell lines (MCF-7, HeLa, and M059 J) was performed using the XTT assay. PM-EO showed 50% inhibition of normal cell growth at 359.8 ± 6.3 μg/mL. Antiproliferative activity was observed against human tumour cell lines, with IC50 values significantly lower than that obtained for the normal cell line, demonstrating IC50 values for MCF-7 cells (254.5 ± 1.6 μg/mL), HeLa cells (324.2 ± 41.4 μg/mL) and M059 J cells (289.3 ± 10.9 μg/mL). Therefore, the cytotoxicity of PM-EO had little influence on the antibacterial effect, since it showed antibacterial activity at lower concentrations. Our results suggest that PM-EO is a promising source of new antibacterial and antitumour agents. 相似文献
995.
E. R. Viana R. M. Rubinger H. A. Albuquerque F. O. Dias A. G. de Oliveira G. M. Ribeiro 《Nonlinear dynamics》2012,67(1):385-392
We report a Periodicity-Detection algorithm, implemented in a LabVIEW routine for real-time data analysis on experimental chaos, to evaluate the periodicity P of experimental time series. The Periodicity-Detector (PD) algorithm was applied to the forced Chua’s circuit with the aim
to build the Periodicity-parameter-space (P-parameter-space). As results of the P-parameter-space, we could observe very complex dynamical behaviors, as regions of periodic structures, a new sequence of
accumulation boundary, and the periodic structures organizing themselves in a period-adding bifurcation cascade. Those results
agree with the maximal Lyapunov exponent and the bifurcation diagram analysis, presented in a previous work. 相似文献
996.
João Paulo Dias Mário Figueira Hermano Frid 《Archive for Rational Mechanics and Analysis》2010,196(3):981-1010
Motivated by Benney’s general theory, we propose new models for short wave–long wave interactions when the long waves are
described by nonlinear systems of conservation laws. We prove the strong convergence of the solutions of the vanishing viscosity
and short wave–long wave interactions systems by using compactness results from compensated compactness theory and new energy
estimates obtained for the coupled systems. We analyze several of the representative examples, such as scalar conservation
laws, general symmetric systems, nonlinear elasticity and nonlinear electromagnetism. 相似文献
997.
M. A. S. Pedroso M. L. Dias C. Azuma C. G. Mothé 《Colloid and polymer science》2000,278(12):1180-1186
This study focused on the preparation of a hydrocarbon dispersion of nanospherical silica using tetraethoxysilane homopolymerization
by a sol–gel process catalyzed by NH4OH in ethanol. The silica surface was rendered hydrophobic by the introduction of trimethylchlorosilane or trimethylethoxysilane
as a terminator. Organophilic particles with diameters in the range 10–130 nm were obtained under controlled conditions. Nevertheless,
the organophilic fraction dispersed in hexane was not greater than 62%. The homopolymerization reaction time was directly
related to the particle size and, in some cases, its insolubility. High terminator concentration and low termination temperature
favored the increase in the number of organophilic particles. The chlorine-containing terminator was more efficient in promoting
the production of hydrocarbon hydrophobic nanospheres.
Received: 21 February 2000/Accepted: 21 June 2000 相似文献
998.
Silvia Russi Helena Pardo Horacio Heinzen Eduardo Dias Patrick Moyna Raúl A. Mariezcurrena Leopoldo Suescun Alvaro W. Mombrú 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):672-673
The structure of the adduct of eucarvone with nitrosobenzene, C16H19NO2, is reported. The [3.2.2] bicyclic system corresponds to two seven‐membered rings in boat and distorted chair conformations and a six‐membered ring that adopts a distorted boat conformation. No conjugation is observed between the phenyl group and the N—O system. The packing is directed mainly by a C?O hydrogen bond, C—H?O‐(1 ? x, ?y, z) and by intermolecular C—H?π interactions. 相似文献
999.
Frédéric Dias Emiliano Renzi Sarah Gallagher Dripta Sarkar Yanji Wei Thomas Abadie Cathal Cummins Ashkan Rafiee 《Acta Mechanica Sinica》2017,33(4):647-662
The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main concerns relevant to the practical use of wave energy converters are sustainability, survivability, and maintainability. Of course, it is also necessary to maximize the capture per unit area of the structure as well as to minimize the cost. In this review, we consider some of the questions related to the topics of sustain-ability, survivability, and maintenance access, with respect to sea conditions, for generic wave energy converters with an emphasis on the oscillating wave surge converter. New analytical models that have been developed are a topic of par-ticular discussion. It is also shown how existing numerical models have been pushed to their limits to provide answers to open questions relating to the operation and characteristics of wave energy converters. 相似文献
1000.
Tavares Célia R. G. Benatti Cláudia T. Dias Filho Benedito P. 《Applied biochemistry and biotechnology》2002,98(1-9):935-945
This study was designed to evaluate the performance of a cylindrical anaerobic digester in treating secondary sewage sludge.
A series of three independent batch experiments was performed for a total operation time of 60 d. The system of anaerobic
digestion showed stability conditions, with no noticeable scum or foaming problems. The chemical oxygen demand reduction reached
29, 21, and 45% in sludge and 95, 85, and 82% in supernatant for the three experiments, respectively. Total coliform bacteria
levels in the digester ranged from 104 to 105 in influent sludge and from 104 to 103 in effluent sludge, with an average reduction of 90%. Fecal coliforms of the order of 104 were enumerated in influent sludge and those of the order of 100 were enumerated in effluent sludge, with an average reduction of 99.9%. The studied system had satisfactory results, showing
that both organic matter and indicator bacteria levels substantially decrease when the sludge is submitted to anaerobic digestion. 相似文献