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Synthesis and measurement of structural and magnetic properties of K-doped LaCoO_3 perovskite materials

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Rare Metals 2010年第5期29卷 491-500页

作者： Manjunath B.Bellakki C.Madhu Tobias Greindl Sandeep Kohli Patrick McCurdy V.Manivannan Department of Mechanical Engineering Colorado State UniversityFort CollinsColoradoUSA Department of Chemistry Colorado State UniversityFort CollinsColoradoUSA

Polycrystalline La1-xKxCoO3 （0≤ x ≤ 0.2） rare earth cobaltates have been synthesized by a solution combustion method using glycine as a fuel. The synthesized ceramic materials were characterized by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, and magnetic measurements and studied for physical properties, such as photoeatalytic activity. FTIR measurements in conjunction with XRD showed that phases beyond 10% K doping are accompanied by small amounts of impurities. Chemical titrations show the presence of Co^4＋ and account for the Co^3＋-Co^4＋ mixed-valency of the system. The parent LaCoO3 shows spin-glass transition at low temperatures, whereas doped samples show transition from spin-glass behavior to paramagnetic ordering on progressive doping of K. ＂Mixed-conductor＂ nature of these ceramics positions them as viable candidates for solid oxide fuel cell （SOFC） applications.

关键词： ceramic materials combustion synthesis X-ray diffraction magnetic properties structural properties

Poly(imine-amide)Hybrid Covalent Adaptable Networks via in situ Oxidation Polymerization

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Chinese Journal of Polymer Science 2023年第10期41卷 1577-1583页

作者： Hong-Xuan Chen Ze-Peng Lei Shao-Feng Huang Huan Jiang Kai Yu Ying-Hua Jin Wei Zhang Department of Chemistry University of Colorado BoulderBoulderColorado80309USA RockyTech Ltd. BoulderColorado80309USA Department of Mechanical Engineering University of Colorado DenverDenverColorado80217USA

Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks(CANs)that have been extensively studied in the past few *** being highly malleable and recyclable,the pioneering polyimine materials are relatively soft and not suitable for certain applications that require high mechanical *** studies have demonstrated the possibility of significantly improving polyimine properties by varying its monomer building blocks,but such component variations are usually not straightforward and can be potentially challenging and ***,we report an in situ oxidation polymerization strategy for preparation of mechanically strong poly(imine-amide)(PIA)hybrid CANs from simple amine and aldehyde *** converting a portion of reversible imine bonds into high-strength amide linkages in situ,the obtained hybrid materials exhibit gradually improved Young’s modulus and ultimate tensile strength as the oxidation level ***,the PIAs remain reprocessable and can be depolymerized into small molecules and oligomers similar as *** work demonstrates the great potential of the in situ transformation strategy as a new approach for development of various mechanically tunable CANs from the same starting building blocks.

关键词： Covalent adaptable networks Polyimine Polyamide In situ oxidation polymerization

El Nio and the Kppen–Geiger Classification: A Prototype Concept and Methodology for Mapping Impacts in Central America and the Circum-Caribbean

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International Journal of Disaster Risk Science 2018年第2期9卷 224-236页

作者： Lino Naranjo Michael H.Glantz Sayat Temirbekov Ivan J.Ramírez Consortium for Capacity Building/INSTAAR University of Colorado Department of Anthropology Colorado State University colorado School of Public Health Colorado State University

The aim of this pilot study conducted by the consortium for capacity building was to develop a prototype concept and methodology for the classification and visualization of the geographic impacts of El Nio on annual climates and seasonality. Our study is based on the Kppen–Geiger climate classification scheme for a set of selected countries affected by strong El Nios in Latin America. By identifying and visualizing the annual and seasonal changes in regional, national, or subnational climate regimes that generally accompany an El Nio event,this research proposes an efficient way to detect and describe climate shifts and variability across time and space. Such knowledge provides a support tool for risk analysis and can potentially enhance government efforts of climate risk management, including disaster risk reduction activities that prevent, mitigate, and improve coping responses to El Nio-related hydrometeorological *** of the conceptual approach and methodology to classifying and mapping El Nio's impacts are described and explained using the Central American and circumCaribbean region as a case study. The potential applications for disaster risk reduction as well as its limitations and future work are also discussed.

关键词： Caribbean Central America Disaster risk reduction El Nio impacts El Nio seasonality Kppen–Geiger classification

Synthesis,and measurement of structural and magnetic properties,of La_(1-x)Na_xFeO_3 (0.0≤x≤0.3) perovskite oxides

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Journal of Rare Earths 2009年第5期27卷 691-697页

作者： Manjunath B.Bellakki Venkatesan Manivannan Patrick McCurdy Sandeep Kohli Department of Mechanical Engineering Colorado State University Department of Chemistry Colorado State University

Polycrystalline La1-xNaxFeO3 (0.0≤x≤0.3) solid solutions were synthesized by a solution combustion method using glycine as a fuel. The combustion synthesized compounds were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffused reflectance (DR) in the UV-vis, and magnetic measurements. The crystal structure examined by X-ray powder diffraction indicated that the samples were single phase and crystallized in an orthorhombic (space group, Pbnm no.62) structure. The parent and sodium-substituted compounds showed canted anti-ferromagnetic behavior associated with an increase in magnetic moment as Na content increased. The changes in magnetic properties of the materials were correlated to the changes in structural features, as shown by Rietveld structural refinement of the materials.

关键词： oxides combustion synthesis X-ray diffraction antiferromagnetic rare earths

Internal valves in populations of Meridion circulare from the A’er Mountain region of northeastern China:Implications for taxonomy and systematics

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Journal of Systematics and Evolution 2011年第5期49卷 486-494页

作者： J.P.KOCIOLEK Department of Ecology and Evolutionary Biology University of Colorado Museum of Natural History University of Colorado

A population of Meridion circulare ***(Greville) *** from Inner Mongolia was found to produce Innenschalen or internal *** of this population with light and scanning electron microscopy showed morphological differentiation between vegetative and spore *** valves typically bear costae and one rimoportula at the *** lack costae and have two rimoportulae,one at the headpole and the other at the *** is plasticity in the production of valve morphologies,and a variety of vegetative valve and spore combinations are *** population of *** *** has initial valves of over 90 μm in length,and all of the initial cells encountered are acostate and bear two *** observations suggest that either spores are the product of sexual reproduction,or that initial valves may be produced parthenogenetically in *** as products of the sexual process have not been reported in diatoms previously,and parthenogenesis in Meridion was reported previously but discounted in other published *** plasticity of valve morphologies expressed in *** ***,between vegetative valves and spores(and back) across a short temporal period suggests that diatoms can alter their cell wall structure dramatically and quickly in response to external variables.

关键词： Bacillariophyceae diatom Innenschalen internal valves Meridion systematics.

Resource discovery in distributed digital libraries through visual knowledge navigation

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2005年第11期6卷 1306-1311页

作者： AHMAD Faisal SUMNER Tamara Department of Computer Science University of Colorado Colorado 80309-0430 USADepartment of Computer Science University of Colorado Colorado 80309-0430 USA

In order to support users to search and browse for various resources, digital libraries are composed of discovery systems which provide user interface and information retrieve system. Recent researches in Information Retrieval have investi- gated different techniques through improving precision and recall to enhance the effectiveness of discovery system in digital libraries. In this paper, we present our work to enhance discovery system effectiveness with a different approach, through resource discovery based on visual knowledge navigation. In our Strand Map Services project under National Science Digital Library, we introduce the visual resource discovery system called conceptual browsing interfaces, to help educators and learners to locate, comprehend and use educational resources in digital libraries. The paper begins with a short introduction of the Strand Map Services. Then we illustrate the service architecture, the design and implementation of its major components. We will focus our discussion of how the visualization system of the Strand Map Services supports the visual knowledge navigation for distributed digital libraries. This includes the knowledge acquisition of the conceptual browsing interfaces, different knowledge representa- tions in the system perspective and user interface perspective, visualization system modules, algorithm and Web services inte- gration to use visual knowledge navigation to enhance resource discovery in digital libraries.

关键词： Discovery system Digital libraries Visualization Concept space Web services

Effects of temperature and hydric environment on survival of the Panamanian Golden Frog infected with a pathogenic chytrid fungus

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Integrative Zoology 2010年第2期5卷 143-153页

作者： Heidi M.BUSTAMANTE Lauren J.LIVO Cynthia CAREY Department of Integrative Physiology University of ColoradoBoulderColoradoUSA

Considerable controversy exists concerning whether or not climate changes(particularly global warming)are causing outbreaks of a lethal amphibian pathogen,the chytrid fungus Batrachochytrium dendrobatidis(Longcore,Pessier&*** 1999).In the present study,groups of Panamanian golden frogs(Atelopus zeteki Dunn,1993),a critically endangered amphibian thought to be nearly extinct in Panama,were exposed to varying dosages of zoospores of Batrachochytrium dendrobatidis,temperatures and hydric environments in order to learn whether this species is susceptible to this pathogen and,if so,how environmental factors affect *** pathogen proved to be highly lethal for *** exposed to a dosage of 100 Bd zoospores survived significantly(P<0.0001)longer than those that had been exposed to 104 or 106 *** frogs housed at 23℃survived significantly(P<0.0001)longer than those that were housed at 17℃.Exposed frogs held in dry conditions survived significantly longer than those in wet conditions(P<0.0001).As a laboratory study,these results do not directly test hypotheses about the relation between climate change and the decline of these frogs in the field,but they inform the discussion about how environmental conditions can have an impact on the interaction between a susceptible amphibian and this *** data do not support the contention that rising global temperatures are necessary to cause the death of amphibians infected with this pathogen because the pathogen was equally lethal at 17 as at 23℃,and frogs at the warmer temperature lived significantly longer than those at the cooler one.

关键词： amphibian declines Atelopus zeteki Batrachochytrium dendrobatidis chytridiomycosis climatelinked-epidemic hypothesis

Quantifying Electrochemical Processes in Batteries and Beyond

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Energy & Environmental Materials 2022年第4期5卷 1001-1004页

作者： Emma N.Antonio Michael F.Toney Materials Science and Engineering Program University of Colorado BoulderBoulderColorado 80309USA Joint Center for Energy Storage Research(JCESR) University of Colorado BoulderBoulderColorado 80309USA Department of Chemical and Biological Engineering University of Colorado BoulderBoulderColorado 80309USA Renewable and Sustainable Energy Institute University of Colorado BoulderBoulderColorado 80309USA

The correlation of electrochemical measurements with materials characterization has advanced our understanding of operation and degradation mechanisms in electrochemical energy storage and many other ***,often these correlations are qualitative,preventing the unambiguous identification of both operational principles and the root causes of performance *** we suggest quantitative approaches to define competing mechanisms and determine their relative *** illustrate the importance of quantitative methodologies over a range of electrochemical systems and highlight the need to consider the effect of the experimental design and measurement *** approaches will reveal the most detrimental degradation mechanisms and enable the development of strategies to suppress,stabilize or eliminate them,leading to materials and devices with longer lifetimes,reduced environmental impact,and improved performance.

关键词： electrochemistry in situ and operando characterization batteries quantification materials science

THE SYNTHESES OF POLYQUINOLINES WITH 2,2'-PYRIDYLQUINOLINE AND 2,6-DIQUINOLYLPYRIDINE AS LIGAND AND THEIR APPLICATIONS IN SOME CATALYTIC REACTIONS

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Chinese Journal of Polymer Science 1989年第4期7卷 360-366页

作者：丁孟贤 TOHNK.STILLE Department of Chemistry Colorado State UniversityFort CollinsColorado 80523 USA

The polyquinolines with 2,2'-pyridylquinoline as bidentate and 2,6-diquinolylpyridine as tridentate ligand have been prepared from 4,4-dlamino- 3,3'-dibenzoyldiphenyl ether, 4,4'-diacetyldiphenyl ether and 1,4-bis (2-acetylpyridyl-6-oxy) benzene, 2,6-diacetylpyridine, respectively. These polyquinoline-supported ligands have been used in hydrogenation and hydroformylation of olefins with some transition metal complexes.

关键词： PYRIDYLQUINOLINE AND 2,6-DIQUINOLYLPYRIDINE AS LIGAND AND THEIR APPLICATIONS IN SOME CATALYTIC REACTIONS THE SYNTHESES OF POLYQUINOLINES WITH 2,2