Glass Transitions Temperature
Mostrando 1-11 de 11 artigos, teses e dissertações.
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1. Photoacoustic spectroscopy applied to glass transition temperature determination of polymers / Aplicação da espectroscopia fotoacústica na determinação da temperatura de transição vítrea de polímeros
Photoacoustic spectroscopy (PAS) is a non-destructive technique and it has been largely applied to the thermal and optical characterization of materials. PAS technique is based on the photoacoustic effect which consist, basically, absorption of a modulated electromagnetic radiation and generation of heat inside of the material studied (sample), by a nonradia
Publicado em: 2010
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2. Propriedades fisicas e transições de fase da banana nanica submetida a secagem com pulso HTST (inicial). / Physical properties and fase transitions of banana nanica on applying an initial HTST drying pulse.
This study was conducted to evaluate the drying of bananas by a high temperature and short time drying pulse combined with hot air-drying process stage at 70°C. Firstly, Portuguese and Brazilian bananas samples were dried and the changes of shrinkage, porosity and structure during drying were analyzed. This results were compared with those obtained in a con
Publicado em: 2007
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3. Reentrant spin glass behavior in polycrystalline La0.7Sr0.3Mn1-X FeX O 3
The magnetic and transport properties of the compound La0.7Sr0.3Mn1-xFe xO 3 (0.1 < x <0.4) have been studied by means of electrical resistivity, AC magnetic susceptibility, and DC magnetization. At low concentrations (x <0.1), the system displays essentially para-to-ferromagnetic transitions as the temperature is decreased, although a decrease in the magnet
Materials Research. Publicado em: 2004-06
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4. Aplicação da calorimetria diferencial da varredura modulada no estudo de blendas polimericas
Temperature modulation was implemented in the differential scanning calorimetry (DSC) in the 1990 s, allowing separation of thermodynamic and kinetic phenomena. In this case, a mathematical treatment of data is necessary. The purpose of this work is to evaluate the application of modulated DSC on the study of polymeric blends made of poli(vinyl alcohol) and
Publicado em: 2001
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5. A Calorimetric Study of the Glass Transition Behaviors in Axes of Bean Seeds with Relevance to Storage Stability.
Although the presence of intracellular aqueous glasses has been established in seeds, their physiological role in storage stability is still conjectural. Therefore, we examined, using differential scanning calorimetry, the thermal behavior of glass transitions in axes of bean (Phaseolus vulgaris L.) with water contents (WC) between 0 and 1 g H2O/g dry weight
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6. Calorimetric Properties of Dehydrating Pollen (Analysis of a Desiccation-Tolerant and an Intolerant Species).
The physical state of water in the desiccation-tolerant pollen of Typha latifolia L. and the desiccation-sensitive pollen of Zea mays L. was studied using differential scanning calorimetry in an attempt to further unravel the complex mechanisms of desiccation tolerance. Melting transitions of water were not observed at water content (wc) values less than 0.2
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7. Periodic structures in lipid monolayer phase transitions
Periodic patterns are observed when supported lipid monolayers doped with low concentrations of fluorescent lipid probes are observed with epi-fluorescence microscopy. Monolayers of dipalmitoyl phosphatidylcholine were examined on air-water interfaces and also on alkylated glass coverslips. The patterns are formed by periodic arrays of solid-phase lipid doma
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8. The Glassy State in Corn Embryos 1
The possibility is examined whether seeds may survive the desiccated state in part by vitrification, or the formation of a glassy state. Embryos excised from viable corn (Zea mays L.) seeds at low moisture contents show a series of low temperature first- and second-order phase transitions in the differential scanning calorimeter. These embryos produce normal
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9. The old problems of glass and the glass transition, and the many new twists.
In this paper I review the ways in which the glassy state is obtained both in nature and in materials science and highlight a "new twist"--the recent recognition of polymorphism within the glassy state. The formation of glass by continuous cooling (viscous slowdown) is then examined, the strong/fragile liquids classification is reviewed, and a new twist-the
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10. The origin of the boson peak and thermal conductivity plateau in low-temperature glasses
We argue that the intrinsic glassy degrees of freedom in amorphous solids giving rise to the thermal conductivity plateau and the “boson peak” in the heat capacity at moderately low temperatures are directly connected to those motions giving rise to the two-level-like excitations seen at still lower temperatures. These degrees of freedom can be thought o
The National Academy of Sciences.
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11. Models of stratum corneum intercellular membranes: 2H NMR of macroscopically oriented multilayers.
Deuterium NMR was used to characterize model membrane systems approximating the composition of the intercellular lipid lamellae of mammalian stratum corneum (SC). The SC models, equimolar mixtures of ceramide:cholesterol:palmitic acid (CER:CHOL:PA) at pH 5.2, were contrasted with the sphingomyelin:CHOL:PA (SPM:CHOL:PA) system, where the SPM differs from the