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Electric,magnetic and microstructural features of the La_(2)CoFeO_(6) lanthanide ferrocobaltite obtained by the modified Pechini route

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journal of Advanced Dielectrics 2021年第3期11卷 16-25页

作者： j.A.jaramillo Palacio K.A.Munoz Pulido j.Arbey Rodríguez D.A.Landínez Téllez j.roa-rojas Grupo de Física de Nuevos Materiales Departamento de Física Universidad Nacional de ColombiaBogotáDCColombia Laboratório de Magnetismo e Materiais Magnéticos Departamento de Física Universidade Federal de Santa Maria Rio Grande do Sul Brazil Grupo de Estudios de Materiales Departamento de Física Universidad Nacional de ColombiaBogotáDCColombia

In the search for new materials with applicable magnetic properties in spintronic devices,the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La_(2)CoFeO_(6) using the modified Pechini route;the experimental study of structural,morphological and magnetic properties,and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional *** refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure,space group P2_(1)/n(#14).Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline,with mean grain sizes between 177 and 188 *** dispersive X-ray spectroscopy suggests that the material obtained contains La,Fe,Co and O in the stoichiometric proportions expected by up to 98%.The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically,showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO_(6) and CoO_(6) *** hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated,up to room temperature.I-V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor *** ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.

关键词： Double perovskite Pechini method crystalline structure ferromagnetic response semiconductor behavior

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AN OPTIMAL CONTROL PROBLEM FOR A LOTKA-VOLTERRA COMPETITION MODEL WITH CHEMO-REPULSION

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Acta Mathematica Scientia 2024年第2期44卷 721-751页

作者： Diana I.HERNÁNDEZ Diego A.RUEDA-GOMEZ Élder j.VILLAMIZAR-roa Universidad Industrial de Santander Escuela de MatemáticasA.A.678BucaramangaColombia

In this paper we study a bilinear optimal control problem for a diffusive Lotka-Volterra competition model with chemo-repulsion in a bounded domain of ℝ^(ℕ),N=2,*** model describes the competition of two species in which one of them avoid encounters with rivals through a chemo-repulsion *** prove the existence and uniqueness of weak-strong solutions,and then we analyze the existence of a global optimal solution for a related bilinear optimal control problem,where the control is acting on the chemical ***,we derive first-order optimality conditions for local optimal solutions using the Lagrange multipliers ***,we propose a discrete approximation scheme of the optimality system based on the gradient method,which is validated with some computational experiments.

关键词： Lotka-Volterra chemo-repulsion optimal control optimality conditions

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Nucleation and growth kinetics of La0.7Sr0.3Cr0.4Mn0.6O3-δ SOFC perovskite:Symmetry alteration evolution induced by Cu2+ and Ni2+ impregnation

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Progress in Natural Science:Materials International 2016年第6期26卷 665-670页

作者： A.Concha-Balderrama G.rojas-George j.Alvarado-Flores H.Esparza-Ponce M.H.Bocanegra-Bernal A.Reyes-rojas Centro de Investigación en Materiales Avanzados S.C.(CIMAV) Laboratorio Nacional de NanotecnologíaMiguel de Cervantes 120 Complejo Industrial ChihuahuaCd.de Chihuahua

La0.7Sr0.3Cr0.4Mn0.6O3-δperovskite nanoparticles have been synthetized using an ethylene glycol modified solgel method and impregnated by Cu0.75Ni0.25nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. Findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D3d6point group symmetry.

关键词： Perovskite structure Sol-gel method Composite Kinetics Rietveld

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Spatial patterns of distribution and abundance of Harrisia portoricensis,an endangered Caribbean cactus

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journal of Plant Ecology 2013年第6期6卷 489-498页

作者： julissa rojas-Sandoval Elvia j.Meléndez-Ackerman Department of Biology University of Puerto RicoRío Piedras CampusPO Box 23360San JuanPuerto Rico 00931-3360USA Center for Applied Tropical Ecology and Conservation University of Puerto RicoPO Box 70377San JuanPuerto Rico 00936-8377USA Department of Environmental Sciences College of Natural SciencesUniversity of Puerto RicoPO Box 70377San JuanPuerto Rico 00936-8377USA

Aims The spatial distribution of biotic and abiotic factors may play a dominant role in determining the distribution and abundance of plants in arid and semiarid *** this study,we evaluated how spatial patterns of microhabitat variables and the degree of spatial dependence of these variables influence the distribution and abundance of the endangered cactus Harrisia *** We used geostatistical analyses of five microhabitat variables(*** cover,soil cover and light incidence)and recorded the abundance of *** in 50 permanent plots established across Mona Island,Puerto Rico,by the United States Department of Agriculture Forest Service as part of the Forest Inventory and Analysis(USDA–FIA).We also used partial Mantel tests to evaluate the relationships between microhabitat variables and abundance of ***,controlling for spatial *** findings Abundance of *** showed strong affinities with microhabitat variables related to canopy structure,soil cover and light *** distribution of this cactus species throughout the island was consistent with the spatial variation patterns of these *** general,landscape-level analyses suggested a predictive value of microhabitat traits for the distribution and abundance of this endangered *** sensitive cacti species,wherein abundance may be influenced by similar variables,these types of analyses may be helpful in developing management plans and identifying critical habitats for conservation.

关键词： abundance Caribbean cactus geostatistics Harrisia portoricensis Mona Island spatial correlation spatial distribution

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Apples to oranges:environmentally derived,dynamic regulation of serotonin neuron subpopulations in adulthood?

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Neural Regeneration Research 2025年第9期20卷 2596-2597页

作者： Christopher j.O’Connell Matthew j.Robson Department of Genetics College of MedicineHarvard UniversityBostonMAUSA james L.Winkle College of Pharmacy Division of Pharmaceutical SciencesUniversity of CincinnatiCincinnatiOHUSA Neuroscience Graduate Program College of MedicineUniversity of CincinnatiCincinnatiOHUSA

Traumatic brain injury(TBI)is a public health problem with an undue economic burden that impacts nearly every age,ethnic,and gender group across the globe(Capizzi et al.,2020).TBIs are often sustained during a dynamic range of exposures to energetic environmental forces and as such outcomes are typically heterogeneous regarding severity and pathology(Capizzi et al.,2020).

关键词： sustained orange dynamic

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Physicochemical properties of Li_(3)Ba_(2)La_(3)(MoO_(4))_(8):Eu,Tb red-emitting phosphor for solid state white lamps

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journal of Rare Earths 2023年第9期41卷 1279-1287,I0001页

作者： Kora Lu rojas Baldivia Gustavo A.Hirata Center for Scientific Research and Higher Education of Ensenada Ensenada Baja California 22860Mexico Center for Nanoscience and Nanotechnology National Autonomous University of Mexico EnsenadaBaja Califomia 22860Mex

In this work,combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light *** synthesized a material with emission wavelength at λ_(em)=617 nm,excited under long UV-blue wavelength based on Eu^(3+),Tb^(3+)-activated molybdates Li_(3)Ba_(2)(La_(1-x-y)Eu_(x)Tb_(y))_(3)(MoO_(4))_(8) with 0 ≤ x ≤1 and 0 ≤ y ≤ 1.A series of powder samples were produced by the combustion method and post-annealed at 800℃ in *** crystalline phase formation was investigated by X-ray diffraction,which reveals the monoclinic C2/c(15) space *** is observed that crystalline structure and morphology are preserved when the host lattice is doped with Eu^(3+) or Tb^(3+) single ions and co-doped with both ions at different doping concentrations.A detailed characterization by scanning electron microscopy(SEM) and transmission electron microscopy(TEM)shows a similar morphology in all samples:rather large(1-7 μm) agglomerate particles with irregular shapes and surrounded by smaller nanoparticles of 50 nm in ***-visible absorption spectra confirm the presence of Eu^(3+) and Tb^(3+) *** luminescent properties of the obtained phosphors were studied in *** measurements indicate that the best emission intensity is for Eu^(3+):Tb^(3+)doping ratios of 80:0,90:0 and 20:*** the other hand,samples with 80:0,60:40,and 20:80 doping ratios show the highest intensity in a detailed photoluminescence analysis and they exhibit the highest quantum yield values.A complete and efficient energy transfer from the sensitizer Tb^(3+) to the activator Eu^(3+) is observed in all co-doped phosphors post-annealed at 800℃ for 4 ***,the Li_(3)Ba_(2)La_(3)(MaO_(4))_(8):Eu^(3+),Tb^(3+) materials fabricated by combustion synthesis are excellent phosphors for being applied as red-emitting component in solid-state white-light lamps due to an improved color rendering index(CRI) that can be obtained under lo

关键词： Molybdate Europium Terbium Luminescence Phosphor-converted LED Rare earths

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Temporal dynamics of neonatal hypoxic-ischemic encephalopathy injuries on magnetic resonance imaging

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Neural Regeneration Research 2025年第11期20卷 3144-3150页

作者： Holly Flyger Samantha j.Holdsworth Alistair j.Gunn Laura Bennet Hamid Abbasi Mātai Medical Research Institute Tairāwhiti GisborneNew Zealand Department of Anatomy&Medical Imaging Faculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand Center for Brain Research The University of AucklandAucklandNew Zealand Auckland Bioengineering Institute The University of AucklandAucklandNew Zealand

Moderate to severe perinatal hypoxic-ischemic encephalopathy occurs in~1 to 3/1000 live births in high-income countries and is associated with a significant risk of death or neurodevelopmental *** assessment is important to help identify highrisk infants,to help families,and to support appropriate interventions.A wide range of monitoring tools is available to assess changes over time,including urine and blood biomarkers,neurological examination,and *** present,magnetic resonance imaging is unique as although it is expensive and not suited to monitoring the early evolution of hypoxic-ischemic encephalopathy by a week of life it can provide direct insight into the anatomical changes in the brain after hypoxic-ischemic encephalopathy and so offers strong prognostic information on the long-term outcome after hypoxic-ischemic *** review investigated the temporal dynamics of neonatal hypoxic-ischemic encephalopathy injuries,with a particular emphasis on exploring the correlation between the prognostic implications of magnetic resonance imaging scans in the first week of life and their relationship to long-term outcome prediction,particularly for infants treated with therapeutic hypothermia.A comprehensive literature search,from 2016 to 2024,identified 20 pertinent *** review highlights that while the optimal timing of magnetic resonance imaging scans is not clear,overall,it suggests that magnetic resonance imaging within the first week of life provides strong prognostic *** challenges limit the timing consistency,particularly the need for intensive care and clinical ***,although most reports examined the prognostic value of scans taken between 4 and 10 days after birth,there is evidence from small numbers of cases that,at times,brain injury may continue to evolve for weeks after *** suggests that in the future it will be important to explore a wider range of times after hypo

关键词： magnetic resonance imaging neonatal hypoxic-ischemic encephalopathy neurodevelopmental outcomes prognostic biomarkers in neuroimaging scan timing therapeutic hypothermia

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Use of two-surfactants mixtures to attain specific HLB values for assisted TPH-diesel biodegradation

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journal of Environmental Sciences 2004年第6期16卷 950-956页

作者： Luis G. Torres Neftalí rojas Rosario Iturbe Instituto de Ingeniería Universidad Nacional Autó noma de México Coordinación de Ingeniería Ambiental Grupo Saneamiento de Suelos y Acuíferos Apartado Postal 70-472 Coyoacán 04510 México D.F. Mexico

In a surfactant assisted biodegradation process, the choice of surfactant(s) is of crucial importance. The question is: does the type of surfactant(i.e. chemical family) affect the biodegradation process at fixed hidrophillic-lypofillic balance(HLB) values? Microcosm assessments were developed using contaminated soil, with around of 5000 mg/kg of hydrocarbons as TPH-diesel. Mixtures of three nonionic surfactants were employed to get a wide range of specific HLB values. Tween20 and Span20 were mixed in the appropriate proportions to get HLB values between 8.6 and 16.7. Tween/Span60 mixtures reached HLB values between 4.7 and 14.9. Finally, Tween/Span80 combinations yielded HLB values between 4.3 and 15. TPH-diesel biodegradation was measured at the beginning, and after 8 weeks, as well as the FCU/gr soil, as a measure of microorganisms′ development during the biodegradation period. A second aim of this work was to assess the use of guar gum as a biodegradation enhancer instead of synthetic products. The conclusions of this work are that surfactant chemical family, and not only the HLB value clearly affects the assisted biodegradation rate. Surfactant's synergism was clearly observed. Regarding the use of guar gum, no biodegradation enhancement was observed for the three assessed concentrations, i.e., 2, 20, and 200 mg/kg, respectively. On the contrary, TPH-diesel removal was lower as the gum concentration increased. It is quite possible that guar gum was used as a microbial substrate.

关键词： aged soils enhanced bioremediation HLB mixtures Tween Span surfactants

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Observation of dipolar transport in one-dimensional photonic lattices

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Science Bulletin 2017年第5期62卷 339-344页

作者： Camilo Cantillano Luis Morales-Inostroza Bastián Real Santiago rojas-rojas Aldo Delgado Alexander Szameit Rodrigo A.Vicencio Departamento de Física MSI-Nucleus on Advanced Opticsand Center for Optics and Photonics(CEFOP)Facultad de CienciasUniversidad de ChileSantiagoChile Center for Optics and Photonics and MSI-Nucleus on Advanced Optics Universidad de ConcepciónCasilla 160-C ConcepcionChile Institute for Physics University of RostockD-18059 RostockGermany

We experimentally study the transport properties of dipolar and fundamental modes on one dimensional(1D) coupled waveguide arrays. By carefully modulating a wide optical beam, we are able to effectively excite dipolar or fundamental modes to study discrete diffraction(single-site excitation) and gaussian beam propagation(multi-site excitation plus a phase gradient). We observe that dipolar modes experience a larger spreading area due to an effective larger coupling constant, which is found to be more than two times larger than the one for fundamental modes. Additionally, we study the effect of non-diagonal disorder and find that while fundamental modes are already trapped on a weakly disorder array, dipoles are still able to propagate across the system.

关键词： Photonic lattices Waveguide arrays Wave propagation Integrated optics

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Amyotrophic lateral sclerosis,a neurodegenerative motor neuron disease with retinal involvement

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Neural Regeneration Research 2022年第5期17卷 1011-1012页

作者： Ana I.Ramírez Rosa de Hoz Pilar rojas juan j.Salazar Instituto de Investigaciones Oftalmológicas Ramón Castroviejo.Universidad Complutense de Madrid MadridSpain Facultad deÓptica y Optometría.Departamento de Inmunología Oftalmología y ORL.Universidad Complutense de MadridMadridSpain Hospital General Universitario Gregorio Marañón Instituto Oftálmico de MadridMadridSpain

Amyotrophic lateral sclerosis(ALS)is a neurodegenerative disease that damages the motor neurons,the spinal cord,the cerebellum,and some areas of the ***,more recent studies show that it can also affect the visual syst... 详细信息

关键词： visual problems involvement

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