Non-paraxial Talbot effect in one-dimensional gratings with period comparable to the wavelength

The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian optics, but when the period of the object is comparable with the wavelength is considered entering its non-paraxial regime. There, it has attracted interest for its applications related to the design of objects and their restorative effects posing in damaged gratings on this scale. In this contribution a study of this phenomenon at level non-paraxial (metaxial) is presented by using scalar diffraction theory in plane waves representation for periodic transversal fields. To this end, a one-dimensional amplitude grating of period p is used which is illuminated by a monochromatic plane wave of wavelength λ where p ranges between 1,5 λ and 4,2 λ.Fil: Arrieta, E.. Universidad Popular del Cesar; ColombiaFil: Bolognini, Nestor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Torres, C.O.. Universidad Popular del Cesar; Colombi

Microstructure, mechanical, and thermogravimetric characterization of cellulosic by-products obtained from biomass seeds

The microstructural, thermal, and nanomechanical characterization of biomass by-products coming from the food industry were studied. Scanning electron microscopy showed a microstructure formed by polygonal grains. The thermal behavior of seeds, evaluated by thermogravimetric analysis, revealed three main components (hemicellulose, cellulose, and lignin). Walnut shell showed the highest thermal stability and also the highest amount of lignin. The nanomechanical aspects were evaluated by nanoindentation. Samples with higher amount of cellulose presented minor modulus values. In accordance with the thermal stability, the highest modulus and hardness were observed in walnut. These by-products could be useful as reinforcement materials for biodegradable plastic industry.This work has been supported by the Spanish Ministry of Science and Innovation (MAT2011-28468-C02-02) and the Autonomous Government of Valencia (Spain) through the research program Geronimo Forteza (62/2010, 9 de Junio DOCV no 6291). M.P. Arrieta is granted by Santiago Grisolia program (GRISOLIA/2011/007).Rayón Encinas, E.; Ferrándiz Bou, S.; Rico Beneito, MI.; López Martínez, J.; Arrieta, MP. (2015). Microstructure, mechanical, and thermogravimetric characterization of cellulosic by-products obtained from biomass seeds. International Journal of Food Properties. 18(6):1211-1222. https://doi.org/10.1080/10942912.2014.884578S1211122218

On a nonlocal moving frame approximation of traveling waves

The profiles of traveling wave solutions of a 1-d reaction-diffusion parabolic equation are transformed into equilibria of a nonlocal equation, by means of an appropriate nonlocal change of variables. In this new formulation both the profile and the propagation speed of the traveling waves emerge as asymptotic limits of solutions of a nonlocal reaction-diffusion problem when time goes to infinity. In this Note we make these results rigorous analyzing the well-posedness and the stability properties of the corresponding nonlocal Cauchy problem. We also analyze its restriction to a finite interval with consistent boundary conditions. For large enough intervals we show that there is an asymptotically stable equilibrium which approximates the profile of the traveling wave in R. This leads to efficient numerical algorithms for computing the traveling wave profile and speed of propagation

Advanced Materials and Manufacturing for Low-Cost, High-Performance Liquid Rocket Combustion Chambers

A document describes the low-cost manufacturing of C103 niobium alloy combustion chambers, and the use of a high-temperature, oxidation-resistant coating that is superior to the standard silicide coating. The manufacturing process involved low-temperature spray deposition of C103 on removable plastic mandrels produced by rapid prototyping. Thin, vapor-deposited platinum-indium coatings were shown to substantially improve oxidation resistance relative to the standard silicide coating. Development of different low-cost plastic thrust chamber mandrel materials and prototyping processes (selective laser sintering and stereolithography) yielded mandrels with good dimensional accuracy (within a couple of mils) for this stage of development. The feasibility of using the kinetic metallization cold-spray process for fabrication of free-standing C1O3 thrusters on removable plastic mandrels was also demonstrated. The ambient and elevated temperature mechanical properties of the material were shown to be reasonably good relative to conventionally processed C103, but the greatest potential benefit is that coldsprayed chambers require minimal post-process machining, resulting in substantially lower machining and material costs. The platinum-iridium coating was shown to provide greatly increased oxidation resistance over the silicide when evaluated through oxyacetylene torch testing to as high as 300 F (= 150 C). The iridium component minimizes reaction with the niobium alloy chamber at high temperatures, and provides the high-temperature oxidation resistance needed at the throat

Efecto Talbot no paraxial en una red unidimensional de periodo comparable a la longitud de onda

The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian optics, but when the period of the object is comparable with the wavelength is considered entering its non-paraxial regime. There, it has attracted interest for its applications related to the design of objects and their restorative effects posing in damaged gratings on this scale. In this contribution a study of this phenomenon at level non-paraxial (metaxial) is presented by using scalar diffraction theory in plane waves representation for periodic transversal fields. To this end, a one-dimensional amplitude grating of period p is used which is illuminated by a monochromatic plane wave of wavelength λ where p ranges between 1,5 λ and 4,2 λ.El efecto Talbot es un fenómeno difractivo ubicado desde su origen en la óptica Gaussiana, pero cuando la longitud de onda es comparable con el periodo del objeto se considera que este efecto entra en su régimen no paraxial, el cual nuevamente ha despertado el interés por su volumen de aplicación relacionado con el diseño de objetos y sus efectos curativo que presenta en redes averiadas a esta escala En esta contribución presentamos un estudio de este fenómeno a nivel no paraxial (metaxial),usando la teoría escalar de difracción en representación de ondas planas para campos periódicos transversal. Para ello se utiliza como objeto periódico una red de amplitud unidimensional de periodo p, iluminada con una onda plana monocromática de amplitud unitaria y longitud de onda λ, donde p se encuentra entre 1,5 λ y 4,2 λ.Centro de Investigaciones Óptica

Efecto Talbot no paraxial en una red unidimensional de periodo comparable a la longitud de onda

The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian optics, but when the period of the object is comparable with the wavelength is considered entering its non-paraxial regime. There, it has attracted interest for its applications related to the design of objects and their restorative effects posing in damaged gratings on this scale. In this contribution a study of this phenomenon at level non-paraxial (metaxial) is presented by using scalar diffraction theory in plane waves representation for periodic transversal fields. To this end, a one-dimensional amplitude grating of period p is used which is illuminated by a monochromatic plane wave of wavelength λ where p ranges between 1,5 λ and 4,2 λ.El efecto Talbot es un fenómeno difractivo ubicado desde su origen en la óptica Gaussiana, pero cuando la longitud de onda es comparable con el periodo del objeto se considera que este efecto entra en su régimen no paraxial, el cual nuevamente ha despertado el interés por su volumen de aplicación relacionado con el diseño de objetos y sus efectos curativo que presenta en redes averiadas a esta escala En esta contribución presentamos un estudio de este fenómeno a nivel no paraxial (metaxial),usando la teoría escalar de difracción en representación de ondas planas para campos periódicos transversal. Para ello se utiliza como objeto periódico una red de amplitud unidimensional de periodo p, iluminada con una onda plana monocromática de amplitud unitaria y longitud de onda λ, donde p se encuentra entre 1,5 λ y 4,2 λ.Centro de Investigaciones Óptica

Impact of leadership on the development of organizational communication

Fundamental leadership in communication has been approached from science as a thematic focus of great relevance both academically and for the industry. In this way, the present study is developed in order to identify the bibliometric applications of the impact of leadership in the development of organizational communication. At the methodological level, a documentary research based on scientometric processes is presented, where the Scopus databases are consulted during the period from 1958 to 2022. The results allow us to show 512 results within the database, observing a significant growth of the scientific prediction, where the most relevant sources are Journal of Business Communication, Corporate Communications, Journal of Communication Management, International Journal of Business Communication and Business Communication Quarterly and in turn observing that 47% of the publications come from the United State

Mixed Vascular Occlusion in a Patient with Interferon-Associated Retinopathy

Interferon (INF)-associated retinopathy occurs in 15–64% of INF-treated patients, transforming this complication into a significant risk for visual impairment. This retinopathy has been described as an ocular complication with a variable clinical course, usually benign and asymptomatic. The most common findings are hemorrhages and cotton wool spots. Atypical ocular side effects include branch or central retinal artery occlusion, central retinal vein occlusion, anterior ischemic optic neuropathy, optic disc edema, neovascular glaucoma and vitreous hemorrhage. Some case series suggest that in most cases the clinical course of the disease is benign, asymptomatic and without long-term consequences and therefore do not recommend any specific treatment; they only recommend the discontinuation of INF in patients with severe manifestations or risk factors such as hypertension or diabetes mellitus. The case reported here presents an atypical manifestation of INF-associated retinopathy consisting of a mixed retinal vascular occlusion (arterial and venous), associated with severe occlusive inflammatory microangiopathy with extensive retinal damage by ischemia and a torpid clinical course despite suspension of treatment. These varieties of occlusive vascular events have not yet been found simultaneously in the literature and neither with an unfavorable clinical course. Although the clinical course of INF-associated retinopathy in most cases is asymptomatic, there may be complications with risk to vision, which is less common. The magnitude and severity of the consequences associated with INF therapy are to be determined in prospective further studies

Enhancing the Thermal Stability of Polypropylene by Blending with Low Amounts of Natural Antioxidants

"This is the peer reviewed version of the following article: Hernández-Fernández, Joaquín, Emilio Rayón, Juan López, and Marina P. Arrieta. 2019. Enhancing the Thermal Stability of Polypropylene by Blending with Low Amounts of Natural Antioxidants. Macromolecular Materials and Engineering 304 (11). Wiley: 1900379. doi:10.1002/mame.201900379, which has been published in final form at https://doi.org/10.1002/mame.201900379. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Natural antioxidants are added in very low amounts to protect a polypropylene (PP) matrix against thermo-oxidative degradation during processing. Thus, PP is melt-blended with caffeic, chlorogenic, trans-ferrulic, and p-coumaric acids, and also with flavone and 3-hydroxyflavone at 0.1 wt% with respect to the PP matrix. Neat PP and PP blended with three traditional antioxidants are prepared for comparison. A complete structural, thermal, and mechanical characterization is conducted. Ferrulic acid and particularly caffeic acid increases the thermal stability, showing also the highest activation energy. The structural changes of PP-based films due to the polymer thermal degradation at high temperature (i.e., 400 degrees C) followed by FTIR reveal that antioxidants effectively delay the thermal degradation process. The wettability and the mechanical performance are also studied to get information regarding the industrial application of such films. While caffeic acid provides a more flexible material, ferrulic acid provides higher water resistance. Finally, AFM-QNM shows that PP with caffeic acid has the highest miscibility.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO), PROMADEPCOL (MAT2017-84909-C2-2-R). M.P.A. thanks MINECO for Juan de la Cierva-incorporación postdoctoral contract (FJCI-2017-33536).Hernández-Fernández, J.; Rayón, E.; López-Martínez, J.; Arrieta, MP. (2019). Enhancing the Thermal Stability of Polypropylene by Blending with Low Amounts of Natural Antioxidants. Macromolecular Materials and Engineering. 304(11):1-13. https://doi.org/10.1002/mame.201900379S1133041

Bacterial Biohybrid Microswimmers

Over millions of years, Nature has optimized the motion of biological systems at the micro and nanoscales. Motor proteins to motile single cells have managed to overcome Brownian motion and solve several challenges that arise at low Reynolds numbers. In this review, we will briefly describe naturally motile systems and their strategies to move, starting with a general introduction that surveys a broad range of developments, followed by an overview about the physical laws and parameters that govern and limit motion at the microscale. We characterize some of the classes of biological microswimmers that have arisen in the course of evolution, as well as the hybrid structures that have been constructed based on these, ranging from Montemagno's ATPase motor to the SpermBot. Thereafter, we maintain our focus on bacteria and their biohybrids. We introduce the inherent properties of bacteria as a natural microswimmer and explain the different principles bacteria use for their motion. We then elucidate different strategies that have been employed for the coupling of a variety of artificial microobjects to the bacterial surface, and evaluate the different effects the coupled objects have on the motion of the 'biohybrid.' Concluding, we give a short overview and a realistic evaluation of proposed applications in the field