On the 2D Dirac oscillator in the presence of vector and scalar potentials in the cosmic string spacetime in the context of spin and pseudospin symmetries

The Dirac equation with both scalar and vector couplings describing the dynamics of a two-dimensional Dirac oscillator in the cosmic string spacetime is considered. We derive the Dirac-Pauli equation and solve it in the limit of the spin and the pseudo-spin symmetries. We analyze the presence of cylindrical symmetric scalar potentials which allows us to provide analytic solutions for the resultant field equation. By using an appropriate ansatz, we find that the radial equation is a biconfluent Heun-like differential equation. The solution of this equation provides us with more than one expression for the energy eigenvalues of the oscillator. We investigate these energies and find that there is a quantum condition between them. We study this condition in detail and find that it requires the fixation of one of the physical parameters involved in the problem. Expressions for the energy of the oscillator are obtained for some values of the quantum number $n$. Some particular cases which lead to known physical systems are also addressed.Comment: 15 pages, 8 figures, matches published versio

Comparison between experimental results and design equations of artificially degraded single step joints

In the case of interventions in existing buildings, the assessment of timber elements and joints, such as the Single Step Joint, is a challenge for engineers, especially when timber presents signs of biological degradation. In this context, many roof structures are subject to unnecessary substitutions due to the lack of knowledge about the behaviour of these types of joints, and specially the consequences of eventual biological attacks. This study aims to evaluate the residual shear strength of Single Step Joints artificially degraded by wood boring insects from the Anobiidae family (e.g. Anobium punctatum). To achieve the established objectives, destructive tests were carried out on undamaged (reference level) and artificially degraded Single Step Joint specimens, varying the level of degradation. The results were analysed in terms of degradation level and compared with the results obtained with design equations for this type of joint found in the literature. From the analysis of the results, it was possible to observe the tendency of reduction of the shear strength with the increase of the degradation level.FCT - Fundação para a Ciência e a Tecnologia(PRT/BD/152833/2021

Gravity-induced vacuum dominance

It has been widely believed that, except in very extreme situations, the influence of gravity on quantum fields should amount to just small, sub-dominant contributions. This view seemed to be endorsed by the seminal results obtained over the last decades in the context of renormalization of quantum fields in curved spacetimes. Here, however, we argue that this belief is false by showing that there exist well-behaved spacetime evolutions where the vacuum energy density of free quantum fields is forced, by the very same background spacetime, to become dominant over any classical energy-density component. This semiclassical gravity effect finds its roots in the infrared behavior of fields on curved spacetimes. By estimating the time scale for the vacuum energy density to become dominant, and therefore for backreaction on the background spacetime to become important, we argue that this vacuum dominance may bear unexpected astrophysical and cosmological implications.Comment: To appear in Phys. Rev. Lett

Small bowel tumors detection in capsule endoscopy by gaussian modeling of color curvelet covariance coefficients

This paper is concerned with the classification of tumoral tissue in the small bowel by using capsule endoscopic images. The followed approach is based on texture classification. Texture descriptors are derived from selected scales of the Discrete Curvelet Transform (DCT). The goal is to take advantage of the high directional sensitivity of the DCT (16 directions) when compared with the Discrete Wavelet Transform (DWT) (3 directions). Second order statistics are then computed in the HSV color space and named Color Curvelet Covariance (3C) coefficients. Finally, these coefficients are modeled by a Gaussian Mixture Model (GMM). Sensitivity of 99% and specificity of 95.19% are obtained in the testing set.Centre Algoritm

The wood moisture factor on the biological deterioration of wooden structures

With sustainability as a growing concern, the rehabilitation of buildings arises as one of the main forms of support for the construction sector. Rehabilitation, in comparison with new construction, is seen as a path to minimize the negative impacts of this activity by reducing, for example, the energy consumption of buildings and its consequent impact on energy production (still meeting the current needs for comfort) and the extraction of raw materials. Wood has a high potential for numerous purposes, also, it is a natural, renewable, and sustainable resource, presenting itself as a promising construction material with enormous importance for the bio-based economy. However, despite being a traditional material, reliable service life prediction of wooden structures continues to be a challenge. Like other biobased materials, wood can be subject to biological deterioration by fungi and insects. The biological agents, when combined with favourable conditions (e.g., temperature, air relative humidity, wood moisture content, etc.), can lead to simply aesthetic damage, reduction in indoor air quality, or compromising its resistant load capacity, creating a risk to human health and safety, in addition to an increase of repair and maintenance costs. Many approaches consider wood moisture content as the key factor to control the activation of the decay process, since fungal colonization of wood requires a minimum moisture content of around 20%. Moreover, though subterranean termites (one of the most damaging wood insects) are able to infest dry wood, contact to moisture is fundamental for effective installation of the colonies. This paper addresses moisture as a conditioning factor in the degradation of wood in construction. The role of water on the development of the biodeterioration processes, the transport of water within wooden elements, as well as how the current normative references address the issue are discussed. Finally, this work presents some of the exiting methods for continuous moisture content monitoring systems that, associated with regular maintenance, can be an alternative to chemical treatments, increasingly limited due to current environmental legislation- (undefined

Score Test for Conditional Independence Between Longitudinal Outcome and Time to Event Given the Classes in the Joint Latent Class Model

Latent class models have been recently developed for the joint analysis of a longitudinal quantitative outcome and a time to event. These models assume that the population is divided in  G  latent classes characterized by different risk functions for the event, and different profiles of evolution for the markers that are described by a mixed model for each class. However, the key assumption of conditional independence between the marker and the event given the latent classes is difficult to evaluate because the latent classes are not observed. Using a joint model with latent classes and shared random effects, we propose a score test for the null hypothesis of independence between the marker and the outcome given the latent classes versus the alternative hypothesis that the risk of event depends on one or several random effects from the mixed model in addition to the latent classes. A simulation study was performed to compare the behavior of the score test to other previously proposed tests, including situations where the alternative hypothesis or the baseline risk function are misspecified. In all the investigated situations, the score test was the most powerful. The methodology was applied to develop a prognostic model for recurrence of prostate cancer given the evolution of prostate-specific antigen in a cohort of patients treated by radiation therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79185/1/j.1541-0420.2009.01234.x.pd

Awaking the vacuum in relativistic stars

Void of any inherent structure in classical physics, the vacuum has revealed to be incredibly crowded with all sorts of processes in relativistic quantum physics. Yet, its direct effects are usually so subtle that its structure remains almost as evasive as in classical physics. Here, in contrast, we report on the discovery of a novel effect according to which the vacuum is compelled to play an unexpected central role in an astrophysical context. We show that the formation of relativistic stars may lead the vacuum energy density of a quantum field to an exponential growth. The vacuum-driven evolution which would then follow may lead to unexpected implications for astrophysics, while the observation of stable neutron-star configurations may teach us much on the field content of our Universe.Comment: To appear in Phys. Rev. Let

Direct determination of Cu and Fe in jet fuel by electrothermal atomic absorption spectrometry with injection of sample as detergent emulsions

AbstractThis paper reports the development of a method for the determination of copper and iron in jet fuels employing the electrothermal atomic absorption spectrometry (ETAAS). In order to allow the direct determination of the analytes, the samples were injected into the graphite furnace as detergent emulsions in order to avoid their volatilization during analysis. The results obtained in this work indicated that a stable emulsion can be formed by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of jet fuel. The injection of emulsions provided integrated absorbance signals with suitable sensitivity and precision for 300min at least. The addition of chemical modifier was not necessary because background values were always very low, allowing the use of pyrolysis temperature around 1000°C for both analytes. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion had remarkable influence on the sensitivity as well as the heating rate employed in the drying step. Under the best conditions established in the present work, limits of detection of 0.50 and 0.46μgL−1 were observed for copper when oil-based and aqueous standards were added to the emulsions for calibration, respectively. For iron, the limits of detection were 0.88 and 0.90μgL−1 for oil-based and aqueous standards, respectively. The method was applied in the determination of Cu and Fe in five samples of jet fuels and a recovery test was performed, producing recovery percentages between 95% and 105%

Quality management practices to direct and control the accomplishment of project objectives in R&D units

Projects create value and capabilities for organizations and beneficiaries of their outcomes and must be managed by implementing quality processes to assure an execution compliant with plans, activities, and applicable standards, and to accomplish the defined requirements and objectives in an efficient and effective manner. This study analyzed the frequency of use of quality management practices by companies with R&D units and compared them with project management students expectations of implementing quality project management practices as a professional. The data was collected using an online survey, and twenty-six quality management practices have been analyzed using descriptive and inferential statistics, following standard procedures, and using the Independent-samples T-Test. For twelve out of the twenty-six practices, significant differences have been found between the two samples, five referring to quality planning practices and seven referring to quality control practices. For the twelve quality management practices, project management students had greater expectations of implementing them, in contrast to the actual frequency of use among the surveyed companies. The results can provide inputs to improve project management practices among companies, reinforcing the importance of training and recruiting project management professionals that have the required training, talent, and aligned expectations on how to successfully manage projects.- (undefined

Effects of anobiid damage on shear strength parallel to the grain in single step joints

ABSTRACT: Traditional carpentry joints can be found worldwide in many timber truss structures connecting rafter and tie beam. One failure mode of this connection result from shear in the tie beam beyond the notch either due to bad design or deterioration. In this article, the reduction in shear strength of Single Step Joints (SSJ) resulting from biological attack by anobiids was analysed. For this purpose, tests were carried out in non-degraded scots pine (Pinus sylvestris L.) specimens (reference) and compared to artificially degraded specimens with three different levels of degradation. The reduction of shear resistance was analysed in relation to the density of holes drilled during the degradation simulation, the loss of mass, and the reduction of the shear-resistant area. At lower degradation levels, no significant reduction in shear strength was observed. On the other hand, the linear regression shows a trend of resistance reduction with increasing degradation. Despite the relatively low coefficient of determination (r2 = 0.25), the parameter that best correlated with the residual strength was the reduction in the shear-resistant area.info:eu-repo/semantics/publishedVersio