1,819 research outputs found
Modification of the Physical Properties of a Nafion Film Due to Inclusion of n-Dodecyltriethylammonium Cation: Time Effect.
This study investigates the effects of modifying commercial Nafion-212 thin films with dodecyltriethylammonium cation (DTA+) on their electrical resistance, elastic modulus, light transmission/reflection and photoluminescence properties. The films were modified through a proton/cation exchange process for immersion periods ranging from 1 to 40 h. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the crystal structure and surface composition of the modified films. The electrical resistance and the different resistive contributions were determined via impedance spectroscopy. Changes in the elastic modulus were evaluated using stress–strain curves. Additionally, optical characterization tests, including light/reflection (250–2000 nm) and photoluminescence spectra, were also performed on both unmodified and DTA+-modified Nafion films. The results reveal significant changes in the electrical, mechanical and optical properties of the films, depending on the exchange process time. In particular, the inclusion of the DTA+ into the Nafion structure improved the elastic behavior of the films by significantly decreasing the Young modulus. Furthermore, the photoluminescence of the Nafion films was also enhanced. These findings can be used to optimize the exchange process time to achieve specific desired properties.Partial funding for open access charge: Universidad de Málag
Nanoporous alumina support covered by imidazole moiety-based ionic liquids: optical characterization and application
This work analyzes chemical surface and optical characteristics of a commercial nanoporous
alumina structure (NPAS) as a result of surface coverage by different imidazolium-based ionic liquids
(1-butyl-3-metylimidazolium hexafluorophosphate, 3-methyl-1-octylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium tetrafluoroborate). Optical characteristics of the IL/NPAS
samples were determined by photoluminescence (at different excitation wavelengths (from 300 nm
to 400 nm), ellipsometry spectroscopy, and light transmittance/reflectance measurements for a range
of wavelengths that provide information on modifications related to both visible and near-infrared
regions. Chemical surface characterization of the three IL/NPAS samples was performed by X-ray
photoelectron spectroscopy (XPS), which indicates almost total support coverage by the ILs. The
IL/NPAS analyzed samples exhibit different photoluminescence behavior, high transparency (<85%),
and a reflection maximum at wavelength ~380 nm, with slight differences depending on the IL, while
the refractive index values are rather similar to those shown by the ILs. Moreover, the illuminated
I–V curves (under standard conditions) of the IL/NPAS samples were also measured for determining
the efficiency energy conversion to estimate their possible application as solar cells. On the other
hand, a computational quantum mechanical modeling method (DFT) was used to establish the most
stable bond between the ILs and the NPAS support.M.A. thanks the SpanishMinistry of Science and Innovation (MCIN/AEI/10.13039/
501100011033) through project PID2021-122613OB-I00
Optical and physicochemical characterizations of a cellulosic/CdSe-QDs@S-DAB5 film
CdSe quantum dots nanoparticles were coated with the thiolated (DiAminoButane based dendrimer) DAB dendrimer of fifth generation (S-DAB(5)) and embedded in a highly hydrophilic regenerated cellulose (RC) film by simple dip-coating method (immersion in QD-dendrimer aqueous solution) as a way to get a flexible nano-engineered film (RC-4/CdSe-QDs@S-DAB(5)) with high transparency and photoluminescence properties for different applications. Optical changes in the RC film associated with QDs inclusion were determined by spectroscopic ellipsometry (SE) measurements, which provide information on changes caused in the refraction index and the extinction coefficients of the film, as well as by light transmittance/reflectance curves and photoluminescence (PL) spectra. Impedance spectroscopy (IS) and other typical physicochemical techniques for material characterization (TEM, SEM and XPS) have also been used in order to have more complete information on film characteristics. A comparison of RC-4/CdSe-QDs@S-DAB(5) film optical characteristics with those exhibited by other RC-modified films depending on the type of dendrimer was also carried out
Influence of TiO2-Coating Layer on Nanoporous Alumina Membranes by ALD Technique
Geometrical, chemical, optical and ionic transport changes associated with ALD of TiO2-coating on the porous structure of two nanoporous alumina membranes (NPAMs), which were obtained by the two-step aluminum anodization method but with different pore size and porosity, are presented. Chemical and morphological changes were determined by analyzing XPS spectra and SEM images, showing practically total coverage of the NPAMs surface and leading to a reduction in the geometrical parameters of both samples, while SAED and high resolution TEM measurements allowed us to determine the crystalline structure and thickness of the TiO2-coating, with the latter confirmed by depth-profile XPS analysis. Spectroscopic ellipsometry measurements were also carried out in order to detect changes in characteristic optical parameters (refractive index, n, and extinction coefficient, k), due to the TiO2-coating of NPAMs. Considering the common application of NPAMs in solute/ion diffusion processes, the effect of the TiO2-coverage on electrochemical parameters was analyzed by measuring the concentration potential with a typical model electrolyte (KCl solutions), leading to an increase of the electropositive character for both kinds of samples
Study of the optical properties of TeO2-PbO-TiO2 glass system
We describe the preparation and some optical properties of high refractive index TeO2-PbO-TiO2 glass system. Highly homogeneous glasses were obtained by agitating the mixture during the melting process in an alumina crucible. The characterization was done by X-ray diffraction, Raman scattering, light absorption and linear refractive index measurements. The results show a change in the glass structure as the PbO content increases: the TeO4 trigonal bipyramids characteristics of TeO2 glasses transform into TeO3 trigonal pyramids. However, the measured refractive indices are almost independent of the glass composition. We show that third-order nonlinear optical susceptibilities calculated from the measured refractive indices using Lines' theoretical model are also independent of the glass composition.361364Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Outcomes of COVID-19 Patients Admitted to the Intermediate Respiratory Care Unit: Non-Invasive Respiratory Therapy in a Sequential Protocol
The intermediate respiratory care units (IRCUs) have a pivotal role managing escalation and de-escalation between the general wards and the intensive care units (ICUs). Since the COVID-19 pandemic began, the early detection of patients that could improve on non-invasive respiratory therapies (NRTs) in IRCUs without invasive approaches is crucial to ensure proper medical management and optimize limiting ICU resources. The aim of this study was to assess factors associated with survival, ICU admission and intubation likelihood in COVID-19 patients admitted to IRCUs. Observational retrospective study in consecutive patients admitted to the IRCU of a tertiary hospital from March 2020 to April 2021. Inclusion criteria: hypoxemic respiratory failure (SpO(2) = 25 rpm with FiO(2) > 50% supplementary oxygen) due to acute COVID-19 infection. Demographic, comorbidities, clinical and analytical data, and medical and NRT data were collected at IRCU admission. Multivariate logistic regression models assessed factors associated with survival, ICU admission, and intubation. From 679 patients, 79 patients (12%) had an order to not do intubation. From the remaining 600 (88%), 81% survived, 41% needed ICU admission and 37% required intubation. In the IRCU, 51% required non-invasive ventilation (NIV group) and 49% did not (non-NIV group). Older age and lack of corticosteroid treatment were associated with higher mortality and intubation risk in the scheme, which could be more beneficial in severe forms. Initial NIV does not always mean worse outcomes
Human Metapneumovirus, Peru
We retrospectively studied 420 pharyngeal swab specimens collected from Peruvian and Argentinean patients with influenzalike illness in 2002 and 2003 for evidence of human metapneumovirus (HMPV). Twelve specimens (2.3%) were positive by multiple assays. Six specimens yielded HMPV isolates. Four of the 6 isolates were of the uncommon B1 genotype
Psychoeducational proposals to promote creativity in educational contexts
En este trabajo se aborda la implementación
de estrategias específicas y la promoción
de un entorno educativo apropiado
para el desarrollo de la creatividad.
Se discute el constructo de creatividad
desde una visión neuropsicológica y se
señala la importancia de que la creatividad
sea incrementada en las prácticas
psicoeducativas, en ambientes desafiantes
y multifacéticos. Se asume que la
estimulación y experimentación precoz
del pensamiento creativo en el contexto educativo son condiciones que favorecen
el desarrollo de las capacidades de resolución
de problemas y desafíos futuros.
Se señalan prácticas de promoción de la
armonía entre la investigación educativa
y la intervención psicológica, en relación
con el desarrollo de capacidades y
actitudes que estimulan el pensamiento
y el potencial creativo
Origin and Epidemiological History of HIV-1 CRF14_BG
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Users must also make clear the license terms under which the work was published. CC BY Licence: http://creativecommons.org/licenses/by/4.0/Background: CRF14_BG isolates, originally found in Spain, are characterized by CXCR4 tropism and rapid disease
progression. This study aimed to identify the origin of CRF14_BG and reconstruct its epidemiological history based on new
isolates from Portugal.Methodology/Principal Findings: C2V3C3 env gene sequences were obtained from 62 samples collected in 1993–1998
from Portuguese HIV-1 patients. Full-length genomic sequences were obtained from three patients. Viral subtypes, diversity,
divergence rate and positive selection were investigated by phylogenetic analysis. The molecular structure of the genomes
was determined by bootscanning. A relaxed molecular clock model was used to date the origin of CRF14_BG. Geno2pheno
was used to predict viral tropism. Subtype B was the most prevalent subtype (45 sequences; 73%) followed by CRF14_BG (8;
13%), G (4; 6%), F1 (2; 3%), C (2; 3%) and CRF02_AG (1; 2%). Three CRF14_BG sequences were derived from 1993 samples.
Near full-length genomic sequences were strongly related to the CRF14_BG isolates from Spain. Genetic diversity of the
Portuguese isolates was significantly higher than the Spanish isolates (0.044 vs 0.014, P,0.0001). The mean date of origin of
the CRF14_BG cluster was estimated to be 1992 (range, 1989 and 1996) based on the subtype G genomic region and 1989
(range, 1984–1993) based on the subtype B genomic region. Most CRF14_BG strains (78.9%) were predicted to be CXCR4.
Finally, up to five amino acids were under selective pressure in subtype B V3 loop whereas only one was found in the
CRF14_BG cluster.Conclusions: CRF14_BG emerged in Portugal in the early 1990 s soon after the beginning of the HIV-1 epidemics, spread to
Spain in late 1990 s as a consequence of IVDUs migration and then to the rest of Europe. CXCR4 tropism is a general
characteristic of this CRF that may have been selected for by escape from neutralizing antibody response
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