84 research outputs found
Neurocriptococose em pacientes com SIDA.
Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de ClÃnica Médica, Curso de Medicina, Florianópolis, 199
Dynamics in Quaternary Ionic Liquids with Non-Flexible Anions: Insights from Mechanical Spectroscopy
The present work investigates how mechanical properties and ion dynamics in ionic
liquids (ILs) can be affected by ILs’ design while considering possible relationships between different
mechanical and transport properties. Specifically, we study mechanical properties of quaternary ionic
liquids with rigid anions by means of Dynamical Mechanical Analysis (DMA). We are able to relate
the DMA results to the rheological and transport properties provided by viscosity, conductivity, and
diffusion coefficient measurements. A good agreement is found in the temperature dependence of
different variables described by the Vogel−Fulcher−Tammann model. In particular, the mechanical
spectra of all the measured liquids showed the occurrence of a relaxation, for which the analysis
suggested its attribution to a diffusive process, which becomes evident when the ion dynamics are
not affected by the fast structural reorganization of flexible anions on a local level
Validação da versão em português da Delirium Ratting Scale revised 98 (DRS-R-98)
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde. Programa de Pós-graduação em Ciências MédicasA escala compreende 16 itens pontuados pelo clÃnico (13 de gravidade e 3 diagnósticos). Foi realizada a tradução da escala para o Português e posterior versão para o Inglês. Após a verificação da validade de face, a escala foi aplicada em cinco grupos de pacientes (n=64) - delirium, depressão, demência, esquizofrenia e outros, por dois avaliadores independentes e cegos ao diagnóstico. O diagnóstico e a avaliação da gravidade, medidos através da escala, foram comparados ao diagnóstico clÃnico, Mini Exame do Estado Mental (MEEM), Confusion Assessment Method (CAM) e Impressão clÃnica global (CGI). Foram realizadas análises para medir validade e confiabilidade. A curva ROC (Receiver Operating Characteristic) foi utilizada para avaliar os melhores pontos de corte para o rastreamento do delirium
Effect of the cation structure on the properties of homobaric imidazolium ionic liquids
In this work we investigate the structure-property relationships in a series of alkylimidazolium ionic liquids with almost identical molecular weight. Using a combination of theoretical calculations and experimental measurements, we have shown that re-arranging the alkyl side chain or adding functional groups results in quite distinct features in the resultant ILs. The synthesised ILs, although structurally very similar, cover a wide spectrum of properties ranging from highly fluid, glass forming liquids to high melting point crystalline salts. Theoretical ab initio calculations provide insight on minimum energy orientations for the cations, which then are compared to experimental X-ray crystallography measurements to extract information on hydrogen bonding and to verify our understanding of the studied structures. Molecular dynamics simulations of the simplest (core) ionic liquids are used in order to help us interpret our experimental results and understand better why methylation of C^{2} position of the imidazolium ring results in ILs with such different properties compared to their non-methylated analogues
Room temperature ionic liquids with two symmetric ions
Room temperature ionic liquids typically contain asymmetric organic cations. The asymmetry is thought to enhance disorder, thereby providing an entropic counter-balance to the strong, enthalpic, ionic interactions, and leading, therefore, to lower melting points. Unfortunately, the synthesis and purification of such asymmetric cations is typically more demanding. Here we introduce novel room temperature ionic liquids in which both cation and anion are formally symmetric. The chemical basis for this unprecedented behaviour is the incorporation of ether-containing side chains – which increase the configurational entropy – in the cation. Molecular dynamics simulations indicate that the ether-containing side chains transiently sample curled configurations. Our results contradict the long-standing paradigm that at least one asymmetric ion is required for ionic liquids to be molten at room temperature, and hence open up new and simpler design pathways for these remarkable materials
Structure-Property Relation of Trimethyl Ammonium Ionic Liquids for Battery Applications
Ionic liquids are attractive and safe electrolytes for diverse electrochemical applications
such as advanced rechargeable batteries with high energy densities. Their properties that are
beneficial for energy storage and conversion include negligible vapor-pressure, intrinsic conductivity
as well as high stability. To explore the suitability of a series of ionic liquids with small ammonium
cations for potential battery applications, we investigated their thermal and transport properties.
We studied the influence of the symmetrical imide-type anions bis(trifluoromethanesulfonyl)imide
([TFSI]−) and bis(fluorosulfonyl)imide ([FSI]−), side chain length and functionalization, as well as
lithium salt content on the properties of the electrolytes. Many of the samples are liquid at ambient
temperature, but their solidification temperatures show disparate behavior. The transport properties
showed clear trends: the dynamics are accelerated for samples with the [FSI]− anion, shorter side
chains, ether functionalization and lower amounts of lithium salts. Detailed insight was obtained
from the diffusion coefficients of the different ions in the electrolytes, which revealed the formation
of aggregates of lithium cations coordinated by anions. The ionic liquid electrolytes exhibit sufficient
stability in NMC/Li half-cells at elevated temperatures with small current rates without the need
of additional liquid electrolytes, although Li-plating was observed. Electrolytes containing [TFSI]−
anions showed superior stability compared to those with [FSI]− anions in battery tests
Afasia global sem hemiparesia: AVC ou transtorno conversivo?
BACKGROUND: The neurologic and psychiatric diagnosis in emergency settings are difficult tasks and require interdisciplinary effort. Conversion disorder is one of the differential diagnosis for certain neurologic disorders. The main characteristic is motor or sensory deficits suggesting neurologic or medical condition, but without organic disease that explains the symptoms. CASE REPORT: We present a 23 year-old-woman with an atypical clinical presentation of stroke: global aphasia without hemiparesis. This patient was initially diagnosed with conversion disorder by the internal medicine service in the emergency room. CONCLUSION: Some rare neurologic diseases can be interpreted as conversive disorders due to some reasons: clinical similarities between the two disorders, unusual clinical presentations, comorbidity of neurologic and psychiatric disorders and psychological features of the neurological patients. Patients presenting with atypical neurological or psychiatric symptoms, in which a diagnosis of conversion disorder is suspected, should always be investigated in an interdisciplinary setting.CONTEXTO: A realização de diagnóstico neurológico e psiquiátrico em ambiente de emergência hospitalar com freqüência é uma tarefa complexa e exige colaboração interdisciplinar. Um dos diagnósticos diferenciais de doenças neurológicas é o transtorno conversivo, cuja caracterÃstica principal é a presença de sintomas afetando funções motoras ou sensoriais, que sugerem desordem clÃnica ou neurológica, porém sem doença orgânica subjacente que explique o quadro. RELATO DE CASO: Os autores relatam o caso de uma paciente de 23 anos com apresentação clÃnica atÃpica de acidente vascular cerebral, afasia global sem hemiparesia, que foi inicialmente diagnosticada como transtorno psiquiátrico pelo serviço de clÃnica médica de emergência. CONCLUSÃO: Certas apresentações neurológicas podem ser interpretadas como transtorno conversivo pelas similaridades clÃnicas entre as duas desordens, raridade do quadro clÃnico, pela presença de sintomatologia psiquiátrica e fatores psicossociais nos pacientes neurológicos. Mesmo com apresentações neurológicas atÃpicas e sintomas psiquiátricos, pacientes com quadro sugestivo de transtorno conversivo devem ser sempre investigados de forma interdisciplinar
Ether functionalisation, ion conformation and the optimisation of macroscopic properties in ionic liquids
Ionic liquids are an attractive material class due to their wide liquid range, intrinsic ionic conductivity, and high chemical as well as electrochemical stability. However, the widespread use of ionic liquids is hindered by significantly higher viscosities compared to conventional molecular solvents. In this work, we show how the transport properties of ionic liquids can be altered significantly, even for isostructural ions that have the same backbone. To this end, structure–property relationships have been determined for a set of 16 systematically varied representative ionic liquids. Variations in molecular structure include ammonium vs. phosphonium, ether vs. alkyl side chains, and rigid vs. flexible anions. Ab initio calculations are used to relate molecular structures to the thermal, structural and transport properties of the ionic liquids. We find that the differences in properties of ether and alkyl functionalised ionic liquids are primarily dependent on minimum energy geometries, with the conformational flexibility of ether side chains appearing to be of secondary importance. We also show unprecedented correlations between anion conformational flexibility and transport properties. Critically, increasing fluidity upon consecutive introduction of ether side chains and phosphonium centres into the cation is found to be dependent on whether the anion is flexible or rigid. We demonstrate that targeted design of functional groups based on structure–property relationships can yield ionic liquids of exceptionally high fluidity
Dynamics, cation conformation and rotamers in guanidinium ionic liquids with ether groups
Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the
exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion
classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications.
We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a
2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are
compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions
and transport properties to estimate the performance and trends of this cation class. The samples with imide-type
anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium
or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the
cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable
temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the
ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations
adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled
conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due
to the coordination of the ether chain as observed by VT-NMR
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Dynamics, cation conformation and rotamers in guanidinium ionic liquids with ether groups
Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications. We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a 2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions and transport properties to estimate the performance and trends of this cation class. The samples with imide-type anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due to the coordination of the ether chain as observed by VT-NMR
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