A numerical analysis of the relation between CTOD and fatigue crack growth

El cálculo de la vida a fatiga durante la etapa de propagación de la grieta se suele realizar relacionando da/dN con ΔK. Sin embargo, la influencia que en estos análisis tiene el parámetro ΔK debe recaer en algún otro parámetro no lineal cercano al frente de la grieta, ya que estos son los que realmente controlan la velocidad de crecimiento de la grieta. El principal objetivo del presente artículo es intentar mejorar la comprensión del crecimiento de grieta en fatiga empleando el desplazamiento de apertura de la punta de la grieta (CTOD). Este parámetro no ha sido muy empleado en el problema del cierre de grieta y su propagación en fatiga, teniendo un gran potencial. Por este motivo, se ha realizado un análisis numérico para un amplio rango de cargas de amplitud constante en dos aleaciones de aluminio (6016-T4 y 6082-T6). Cuando no se considera el contacto entre los flancos de la grieta se puede observar una relación bien definida entre el valor máximo de CTOD y ΔK, lo cual indica que no existe influencia de la relación de cargas y valida la mecánica de la fractura elástica lineal. Se ha encontrado una relación lineal entre los valores de CTOD y ΔK al considerar una doble escala logarítmica. Los valores de CTOD cuando se considera el contacto se superpone a los resultados sin contacto, únicamente cuando se emplea el ΔK efectivo, lo cual valida el concepto del cierre de grieta. Se ha encontrado una relación lineal entre da/dN y CTOD cuando se considera una doble escala logarítmica para la aleación de aluminio 6082-T6.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Isobaric vapor−liquid equilibrium data for binary system of glycerol ethyl acetal and acetonitrile at 60.0 kPa and 97.8 kPa

Isobaric vapor−liquid equilibrium (VLE) data for the binary mixture of glycerol ethyl acetal (GEA) and acetonitrile were measured at 60.0 kPa and 97.8 kPa, using a dynamic recirculating still. The VLE data were correlated using the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models, and the interaction parameters of this mixture were estimated. The experimental procedure was checked by measuring VLE data at 97.8 kPa of the well known system acetone/methanol showing high conformity, as given by applying a set of VLE consistency tests. The vapor pressure of GEA was measured, for the first time, in the temperature range from 371.85 K to 456.85 K, and it is described by the following expression: ln PGEA sat (Pa) = 24.17 − 5781/T(K). The information collected is of utmost importance for the purification of GEA synthesized using simulated moving bed reactor technology

Coupled PermSMBR – Process design and development for 1,1-dibutoxyethane production

AbstractIn this work, a new configuration of the simulated moving bed membrane reactor (PermSMBR) technology is presented, the coupled PermSMBR, where the tubular membranes are located after fixed-bed columns packed with the catalyst/adsorbent. By this way the membranes are not in contact with the solid, which from an industrial point of view is easier to implement since the process of membranes installation/replacement and clean-up is simpler than in the previous considered set-up (tubular membranes packed with the catalyst/adsorbent – integrated PermSMBR). The 1,1-dibutoxyethane production is used, as an example, and the features of the new “coupled PermSMBR” and the previous set-up (integrated PermSMBR) are discussed. The coupled PermSMBR revealed to be a very attractive solution for the sustainable 1,1-dibutoxyethane production, proved by the high productivity and low desorbent consumption obtained within the studied conditions

Quantum Conductance in Silver Nanowires: correlation between atomic structure and transport properties

We have analyzed the atomic arrangements and quantum conductance of silver nanowires generated by mechanical elongation. The surface properties of Ag induce unexpected structural properties, as for example, predominance of high aspect ratio rod-like wires. The structural behavior was used to understand the Ag quantum conductance data and the proposed correlation was confirmed by means of theoretical calculations. These results emphasize that the conductance of metal point contacts is determined by the preferred atomic structures and, that atomistic descriptions are essential to interpret the quantum transport behavior of metal nanostructures.Comment: 4 pages, 4 figure

Perspetivas de utilização de nanomateriais em nanodiagnóstico

Conventional diagnostic methods are exclusively focused on the detection of the symptoms associated to a given pathology. Any process able to determine with anticipation the occurrence of a disease, inclusively before the first symptoms, or providing the means to predict the possibility of occurrence of that disease, would significantly reinforce the effectiveness of the therapy allowing, at the same time, the establishment of prevention measures to avoid its progression. Much of the worldwide health research aims at the development of expedite devices or strategies capable of carrying out the monitoring of first level signs, or able to early detect and quantify biomarkers, usually at very low concentrations, associated to a given illness. In the search for alternative diagnostic methods able to overcome the limitations of available technology nanomaterials assume a decisive role and anticipate extremely promising developments in healthcare medicine. Os métodos de diagnósticos convencionais estão exclusivamente empenhados na deteção de sintomas associados a uma dada patologia. Qualquer processo que permita determinar o mais antecipadamente possível a ocorrência da doença, inclusive antes de surgirem os primeiros indícios, ou que permita avaliar o risco da doença ocorrer, reforçaria significativamente as hipóteses de sucesso da terapia e tornaria até praticável tomar medidas preventivas para evitar a sua progressão. Muita da investigação em curso na área da medicina passa pelo desenvolvimento de estratégias ou dispositivos capazes de efetuar a monitorização, o mais antecipadamente possível, destes indícios, ou então capazes de detetar e quantificar precocemente marcadores biológicos, usualmente em concentrações muito baixas, associados a uma dada patologia. Na pesquisa por métodos de diagnósticos alternativos, aptos a ultrapassar algumas das limitações dos métodos atuais, os nanomateriais assumem um papel decisivo e abrem perspetivas de desenvolvimento extremamente promissoras para a área do nanodiagnóstico.

Human leucocyte antigen profile in patients with aids and cytomegalovirus retinitis with and without macular involvement

Introduction: Cytomegalovirus retinitis is one of AIDS ocular manifestations. The objective of the present study was to determine possible associations between class I and II HLA antigens and alleles in patients with AIDS and cytomegalovirus retinitis (CMV-R) with macular involvement.Method: The study population consisted of 22 patients with AIDS and CMV-R with macular involvement (Group I), 19 patients with AIDS and CMV-R without macular involvement (Group II), and 202 individuals with negative serology for human immunodeficiency virus (Group III - control). Class I HLA antigens were typed by classical serology. Class II alleles were identified using sequence-specific oligonucleotide primers hybridized with amplified DNA. Results: HLA-DRB1*14 and  HLA-DRB1*10 specificities were more frequent among patients with macular involvement, possibly indicating greater susceptibility to this condition. In contrast, the HLA-B35 antigen may be associated with protection against macular involvement since it was significantly more frequent among patients without this involvement.Conclusions: The HLA-DRB1*14 and HLA-DRB1*10  alleles may favor the development of CMV-R with macular involvement, whereas the HLA-B35 subtype may be associated with protection against macular involvement

The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed neutrinos

We implement the seesaw mechanism in the 3-3-1 model with right-handed neutrinos. This is accomplished by the introduction of a scalar sextet into the model and the spontaneous violation of the lepton number. We identify the Majoron as a singlet under $SU_L(2)\otimes U_Y(1)$ symmetry, which makes it safe under the current bounds imposed by electroweak data. The main result of this work is that the seesaw mechanism works already at TeV scale with the outcome that the right-handed neutrino masses lie in the electroweak scale, in the range from MeV to tens of GeV. This window provides a great opportunity to test their appearance at current detectors, though when we contrast our results with some previous analysis concerning detection sensitivity at LHC, we conclude that further work is needed in order to validate this search.Comment: about 13 pages, no figure

Non-vacuum Solutions of Bianchi Type VI_0 Universe in f(R) Gravity

In this paper, we solve the field equations in metric f(R) gravity for Bianchi type VI_0 spacetime and discuss evolution of the expanding universe. We find two types of non-vacuum solutions by taking isotropic and anisotropic fluids as the source of matter and dark energy. The physical behavior of these solutions is analyzed and compared in the future evolution with the help of some physical and geometrical parameters. It is concluded that in the presence of isotropic fluid, the model has singularity at $\tilde{t}=0$ and represents continuously expanding shearing universe currently entering into phantom phase. In anisotropic fluid, the model has no initial singularity and exhibits the uniform accelerating expansion. However, the spacetime does not achieve isotropy as $t\rightarrow\infty$ in both of these solutions.Comment: 20 pages, 5 figures, accepted for publication in Astrophys. Space Sc