470 research outputs found
Anisotropy in nanocellular polymers promoted by the addition of needle‐like sepiolites
This work presents a new strategy for obtaining nanocellular materials with high anisotropy ratios by means of the addition of needle‐like nanoparticles. Nanocellular polymers are of great interest due to their outstanding properties, whereas anisotropic structures allow the realization of improved thermal and mechanical properties in certain directions. Nanocomposites based on poly(methyl methacrylate) (PMMA) with nanometric sepiolites are generated by extrusion. From the extruded filaments, cellular materials are produced using a two‐step gas dissolution foaming method. The effect of adding various types and contents of sepiolites is investigated. As a result of the extrusion process, the needle‐like sepiolites are aligned in the machine direction in the solid nanocomposites. Regarding the cellular materials, the addition of sepiolites allows one to obtain anisotropic nanocellular polymers with cell sizes of 150 to 420 nm and cell nucleation densities of 1013–1014 nuclei cm−3 and presenting anisotropy ratios ranging from 1.38 to 2.15, the extrusion direction being the direction of the anisotropy. To explain the appearance of anisotropy, a mechanism based on cell coalescence is proposed and discussed. In addition, it is shown that it is possible to control the anisotropy ratio of the PMMA/sepiolite nanocellular polymers by changing the amount of well‐dispersed sepiolites in the solid nanocomposites
Performance Evaluation of Single-Channel Receivers for Wireless Optical Communications by Numerical Simulations
Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes
The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N<sub>2</sub>, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, k<sub>Cl</sub>±2σ (in units of cm<sup>3</sup> molecule<sup>−1</sup> s<sup>−1</sup>) were: trans-2-pentenal (1.31±0.19)×10<sup>−10</sup>; trans-2-hexenal (1.92±0.22)×10<sup>−10</sup>; trans-2-heptenal (2.40±0.29)×10<sup>−10</sup>; n-pentanal (2.56±0.27)×10<sup>−10</sup>; n-hexanal (2.88±0.37)×10<sup>−10</sup>; n-heptanal (3.00±0.34)×10<sup>−10</sup>. <P style='line-height: 20px;'> Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO<sub>3</sub> radicals
Contribución al estudio de la entomofauna del Monte del Estado Selladores-Contadero (Jaén)
By sundry capture methods it is achieved an insect collecting in 6 plots that are located in Monte de Selladores-Contadero, Jaén (Spain). The taxonomic analysis about 4.787 specimen gives as a result the identification of 275 species belonging at 12 Orders and 82 Families.Mediante diversos métodos de captura se realiza una recolección de insectos en 6 parcelas ubicadas en el Monte de Selladores-Contadero (Jaén). El análisis taxonómico sobre 4.787 especímenes, ofrece como resultado la identificación de 275 especies correspondientes a 12 Órdenes y 82 Familias
Quasiparticle energies for large molecules: a tight-binding GW approach
We present a tight-binding based GW approach for the calculation of
quasiparticle energy levels in confined systems such as molecules. Key
quantities in the GW formalism like the microscopic dielectric function or the
screened Coulomb interaction are expressed in a minimal basis of spherically
averaged atomic orbitals. All necessary integrals are either precalculated or
approximated without resorting to empirical data. The method is validated
against first principles results for benzene and anthracene, where good
agreement is found for levels close to the frontier orbitals. Further, the size
dependence of the quasiparticle gap is studied for conformers of the polyacenes
() up to n = 30.Comment: 10 pages, 5 eps figures submitted to Phys. Rev.
Physical activity and bone health in schoolchildren: the mediating role of fitness and body fat
This is the final version of the article. Available from Public Library of Science via the DOI in this record.BACKGROUND: The relationship between physical activity (PA) and bone health is well known, although the role of percent body fat (%BF) and fitness as confounders or mediators in this relationship remains uncertain. OBJECTIVE: To examine whether the association between PA and bone mineral content (BMC) is mediated by %BF and cardiorespiratory fitness (CRF). METHODS: In this cross sectional study, BMC, total %BF (by DXA), vigorous PA (VPA), CRF, age and height were measured in 132 schoolchildren (62 boys, aged 8-11 years). ANCOVA was used to test differences in BMC by %BF, CRF and VPA, controlling for different sets of confounders. Simple mediation analyses and serial multiple mediation analyses were fitted to examine whether the relationship between PA and BMC is mediated by %BF and fitness. RESULTS: Children with high %BF had higher total body BMC than their peers after controlling for all sets of confounders. Children with good CRF or VPA had significantly less total body BMC after controlling for age and sex but in children with good CRF this inverse relation disappeared after adjusting by %BF. %BF and CRF both act as a full mediator in the association between VPA and BMC, after inclusion of the potential confounders in the models. CONCLUSION: Fitness and %BF seem to have a mediator role on the relationship between physical activity and bone mass.This study was funded by grant numbers PII1I09-0259-9898 and POII10-0208-5325 from the Ministry of Education and Science - Junta de Comunidades de Castilla-La Mancha, and Ministry of Health (FIS grant number PI081297). Additional funding was provided by the Research Network on Preventative Activities and Health Promotion (RD06/0018/0038)
Accurate detection and quantification of SARS-CoV-2 genomic and subgenomic mRNAs by ddPCR and meta-transcriptomics analysis
SARS-CoV-2 replication requires the synthesis of a set of structural proteins expressed through discontinuous transcription of ten subgenomic mRNAs (sgmRNAs). Here, we have fine-tuned droplet digital PCR (ddPCR) assays to accurately detect and quantify SARS-CoV-2 genomic ORF1ab and sgmRNAs for the nucleocapsid (N) and spike (S) proteins. We analyzed 166 RNA samples from anonymized SARS-CoV-2 positive subjects and we observed a recurrent and characteristic pattern of sgmRNAs expression in relation to the total viral RNA content. Additionally, expression profiles of sgmRNAs, as determined by meta-transcriptomics sequencing of a subset of 110 RNA samples, were highly correlated with those obtained by ddPCR. By providing a comprehensive and dynamic snapshot of the levels of SARS-CoV-2 sgmRNAs in infected individuals, our results may contribute a better understanding of the dynamics of transcription and expression of the genome of SARS-CoV-2 and facilitate the development of more accurate molecular diagnostic tools for the stratification of COVID-19 patients
Eudragit® L100/chitosan composite thin bilayer films for intravaginal pH-responsive release of Tenofovir
[EN] The high rate of HIV new infections and AIDS-related deaths each year make prevention tools still necessary today. Different dosage forms – including films – for vaginal administration of antiretroviral drugs have been developed for this purpose. Six batches of Tenofovir-loaded films were formulated based on Eudragit® L100 (EL100) and chitosan, containing triethyl citrate and glycerol. In all the cases films structured in two layers – the upper layer mainly attributed to EL100 and the lower layer to chitosan – were revealed by SEM. A higher content in EL100 and plasticizers improves the mechanical properties and control over drug release in the vaginal medium without affecting mucoadhesion. The EL100-based layer acts as a structuring agent that controls Tenofovir release for days in the vaginal medium while it occurs in a few hours in the presence of seminal fluid. Bilayer films with the highest tested content of EL100 and plasticizers would be the most suitable as vaginal microbicides as they are easier to administer due to their excellent mechanical properties and they offer more comfortable posology and enhanced protection against HIV during intercourse due to their pH-responsive release of Tenofovir.This work was supported by the Spanish Research Agency and the European Regional Development Fund (AEI/FEDER, UE) [MAT2016-76416-R]
Microcalcificaciones mamarias. Frecuencia, manejo y evolución en el Consultorio de Mastología del Servicio de Cirugía General-HCIPS
Las microcalcificaciones mamarias son las lesiones no palpables de la mama más frecuentes. Se revisaron de forma retrospectiva todas las fichas clínicas de las pacientes con lesiones mamarias no palpables visualizadas por mamografía, que concurrieron de febrero a diciembre del año 2001 al Consultorio de Mastología del Hospital Central del Instituto de Previsión Social (HCIPS). Se estudiaron las pacientes que presentaban microcalcificaciones quienes fueron clasificadas y tratadassiguiendo las pautas del Colegio Americano de Radiología. Las pacientes de alta sospecha y las de intermedia con antecedentes familiares de cáncer de mama, fueron sometidas a biopsia radioquirúrgica. En las de baja e intermedia probabilidad de malignidad sin antecedentes familiares, se adoptó una conducta conservadora. De las 106 pacientes con lesiones no palpables de la mama, 78 presentaron microcalcificaciones, de ellas 36 (46,2%) fueron de baja, 9 (11,6%) de intermedia, y 33 (42,2%) de alta sospecha de malignidad. Al inicio del estudio, 36 pacientes y a los seis meses 12 más (seis de baja probabilidad y seis de intermedia sin antecedentes familiares) fueron sometidas a biopsia radio-quirúrgica. Los hallazgos anátomo-patológicos demostraron carcinoma mamario en 24 casos (50%), cuatro de ellos invasores (tres con axila comprometida) y 20 no invasores. Las microcalcificaciones mamarias fueron el hallazgo radiológico más común entre las lesiones no palpables de la mama. Su reconocimiento y caracterización es elemental para detectar precozmente patologías malignas de la mama
Effect of the Front and Back Illumination on Sub-Terahertz Detection Using n-Channel Strained-Silicon MODFETs
[EN] Plasma waves in semiconductor gated 2-D systems can be used to efficiently detect Terahertz (THz) electromagnetic radiation. This work reports on the response of a strained-Si Modulation-doped Field-Effect Transistor (MODFET) under front and back sub-THz illumination. The response of the MODFET has been characterized using a two-tones solid-state continuous wave source at 0.15 and 0.30 THz. The DC drain-to-source voltage of 500-nm gate length transistors transducing the sub-THz radiation (photovoltaic mode) exhibited a non-resonant response in agreement with literature results. Two configurations of the illumination were investigated: (i) front side illumination in which the transistor was shined on its top side, and (ii) back illumination side where the device received the sub-THz radiation on its bottom side, i.e., on the Si substrate. Under excitation at 0.15 THz clear evidence of the coupling of terahertz radiation by the bonding wires was found, this coupling leads to a stronger response under front illumination than under back illumination. When the radiation is shifted to 0.3 THz, as a result of a lesser efficient coupling of the EM radiation through the bonding wires, the response under front illumination was considerably weakened while it was strengthened under back illumination. Electromagnetic simulations explained this behavior as the magnitude of the induced electric field in the channel of the MODFET was considerably stronger under back illumination.This research was funded by the Ministerio de Ciencia, Investigacion y Universidades of Spain andFEDER (ERDF: European Regional Development Fund) under the Research Grants numbers RTI2018-097180-B-100 and TEC2016-78028-C3-3-P and FEDER/Junta de Castilla y Leon Research Grant number SA256P18. Also by Conselleria d'Educacio, lnvestigacio, Cultura i Esport, Generalitat Valenciana (Spain) through the grant AIC0/2019/018. The APC received no external funding.Delgado-Notario, JA.; Calvo-Gallego, J.; Velázquez-Pérez, JE.; Ferrando Bataller, M.; Fobelets, K.; Meziani, YM. (2020). Effect of the Front and Back Illumination on Sub-Terahertz Detection Using n-Channel Strained-Silicon MODFETs. Applied Sciences. 10(17):1-9. https://doi.org/10.3390/app10175959S191017Lewis, R. A. (2019). A review of terahertz detectors. Journal of Physics D: Applied Physics, 52(43), 433001. doi:10.1088/1361-6463/ab31d5Dragoman, D., & Dragoman, M. (2004). Terahertz fields and applications. Progress in Quantum Electronics, 28(1), 1-66. doi:10.1016/s0079-6727(03)00058-2Mittleman, D. M. (2017). Perspective: Terahertz science and technology. Journal of Applied Physics, 122(23), 230901. doi:10.1063/1.5007683Pawar, A. Y., Sonawane, D. D., Erande, K. B., & Derle, D. V. (2013). 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