Importance of considering a material micro-failure criterion in the numerical modelling of the shot peening process applied to parabolic leaf springs

Shot peening is a cold-working mechanical process in which a shot stream is propelled against a component surface. Its purpose is to introduce compressive residual stresses on component surfaces for increasing the fatigue resistance. This process is widely applied in springs due to the cyclical loads requirements. This paper presents a numerical modelling of shot peening process using the finite element method. The results are compared with experimental measurements of the residual stresses, obtained by the X-rays diffraction technique, in leaf springs submitted to this process. Furthermore, the results are compared with empirical and numerical correlations developed by other authors.

Intrinsic colony conditions affect the provisioning and oviposition process in the stingless bee Melipona scutellaris

The cell provisioning and oviposition process (POP) is a unique characteristic of stingless bees (Meliponini), in which coordinated interactions between workers and queen regulate the filling of brood cells with larval resources and subsequent egg laying. Environmental conditions seem to regulate reproduction in stingless bees; however, little is known about how the amount of food affects quantitative sequences of the process. We examined intrinsic variables by comparing three colonies in distinct conditions (strong, intermediate and weak state). We predicted that some of these variables are correlated with temporal events of POP in Melipona scutellaris colonies. The results demonstrated that the strong colony had shorter periods of POP.

Photolysis of ferric ions in the presence of sulfate or chloride ions: implications for the photo-Fenton process

The photo-Fenton process (Fe(2+)/Fe(3+), H(2)O(2), UV light) is one of the most efficient and advanced oxidation processes for the mineralization of the organic pollutants of industrial effluents and wastewater. The overall rate of the photo-Fenton process is controlled by the rate of the photolytic step that converts Fe(3+) back to Fe(2+). In this paper, the effect of sulfate or chloride ions on the net yield of Fe(2+) during the photolysis of Fe(3+) has been investigated in aqueous solution at pH 3.0 and 1.0 in the absence of hydrogen peroxide. A kinetic model based on the principal reactions that occur in the system fits the data for formation of Fe(2+) satisfactorily. Both experimental data and model prediction show that the availability of Fe(2+) produced by photolysis of Fe(3+) is inhibited much more in the presence of sulfate ion than in the presence of chloride ion as a function of the irradiation time at pH 3.0.

Data collapse, scaling functions, and analytical solutions of generalized growth models

We consider a nontrivial one-species population dynamics model with finite and infinite carrying capacities. Time-dependent intrinsic and extrinsic growth rates are considered in these models. Through the model per capita growth rate we obtain a heuristic general procedure to generate scaling functions to collapse data into a simple linear behavior even if an extrinsic growth rate is included. With this data collapse, all the models studied become independent from the parameters and initial condition. Analytical solutions are found when time-dependent coefficients are considered. These solutions allow us to perceive nontrivial transitions between species extinction and survival and to calculate the transition's critical exponents. Considering an extrinsic growth rate as a cancer treatment, we show that the relevant quantity depends not only on the intensity of the treatment, but also on when the cancerous cell growth is maximum.

Effects of Laser on the Synovial Fluid in the Inflammatory Process of the Knee Joint of the Rabbit

Objective: The purpose of this study was to evaluate the effects of low-level laser (LLL) energy on the clinical signs of inflammation and the cellular composition of synovial fluid (SF) in the inflamed knee of the rabbit. Background Data: There are few findings related to the effects of LLL on SF in inflammatory processes and there is little knowledge about the optimal parameters for reducing joint inflammation. Materials and Methods: Inflammation in the right knee of 36 rabbits was induced by intracapsular injection (0.2 mL) of Terebinthina commun (Tc). The animals were randomly assigned to three groups: acute experimental group (AEG), chronic experimental group (CEG), and control group (CG), which only received Tc. Each group was divided in two subgroups of six animals each. The AEG and CEG groups began to receive laser treatment 2 and 5 d after the induction of inflammation, respectively. Laser irradiation at a wavelength of 830 nm, power output of 77 mW, and power density of 27.5 W/cm(2) was applied daily for 7 d for either 0.12 sec or 0.32 sec, resulting in doses of 3.4 J/cm(2) and 8 J/cm(2), respectively. Body mass, joint perimeter, joint temperature, and the morphology of the SF were analyzed. Results: There was no statistically significant differences between groups in the body mass, joint perimeter, and SF morphology. Conclusion: Laser irradiation with the selected parameters produced only a few subtle differences in the inflammatory signs and the SF. The lack of effects may have been due to the short irradiation time.

Evaluation of Laser Phototherapy in the Inflammatory Process of the Rat's TMJ Induced by Carrageenan

Aim: The aim of this study was to evaluate, by light microscopy, the effects of laser phototherapy (LPT) at 780nm or a combination of 660 and 790 nm, on the inflammatory process of the rat temporomandibular joint (TMJ) induced by carrageen. Background: Temporomandibular disorders (TMDs) are frequent in the population and generally present an inflammatory component. Previous studies have evidenced positive effects of laser phototherapy on TMDs. However, its mechanism of action on the inflammation of the TMJ is not known yet. Materials and Methods: Eighty-five Wistar rats were divided into 9 groups: G1, Saline; G2, Saline + LPT IR; G3, Saline + LPT IR + R; G4, Carrageenan; G5, Carrageenan + LPT IR; G6, Carrageenan + LPT IR + R; G7, previous LPT + Carrageenan; G8, previous LPT + carrageenan + LPT IR; and G9, previous LPT + carrageenan + LPT IR + R, and then subdivided in subgroups of 3 and 7 days. After animal death, specimens were taken, routinely cut and stained with HE, Sirius Red, and Toluidine Blue. Descriptive analysis of components of the TMJ was done. The synovial cell layers were counted. Results: Injection of saline did not produced inflammatory reaction and the irradiated groups did not present differences compared to non-irradiated ones. After carrageenan injection, intense inflammatory infiltration and synovial cell layers proliferation were observed. The infrared irradiated group presented less inflammation and less synovial cell layers number compared to other groups. Previous laser irradiation did not improve the results. Conclusion: It was concluded that the LPT presented positive effects on inflammatory infiltration reduction and accelerated the inflammation process, mainly with IR laser irradiation. The number of synovial cell layers was reduced on irradiated group.

A Paradigm Shift in Predoctoral Dental Curricula in Brazil: Evaluating the Process of Change

In 2002, the Brazilian Ministry of Education approved the official curricular guidelines for undergraduate courses in Brazil to be adopted by the nation's 188 dental schools. In 2005-06, the Brazilian Dental Education Association (BDEA) promoted workshops in forty-eight of the schools to verify the degree of transformation of the curriculum based on these guidelines. Among the areas analyzed were course philosophy (variables were v1: knowledge production based on the needs of the Brazilian Public Health System [BPHS]; v2: health determinants; and v3: postgraduate studies and permanent education); pedagogical skills (v4: curricular structure; v5: changes in pedagogic and didactic skills; and v6: course program orientation); and dental practice scenarios (v7: diversity of the scenarios for training/learning; v8: academic health care centers opened to the BPHS; and v9: participation of students in health care delivery for the population). The subjects consisted of faculty members (n=711), students (n=228), and employees (n=14). The results showed an incipient degree of curriculum transformation. The degree of innovation was statistically different depending on the type of university (public or private) for variables I, 2, 4, 5, 6, and 7. Private schools reported a higher level of innovation than public institutions. Resistance to transforming the dental curriculum according to the official guidelines may be linked to an ideological conception that supports the private practice model, continues to have faculty members direct all classroom activities, and prevents students from developing an understanding of professional practice as targeted towards the oral health needs of all segments of society.

Confronting dark energy models using galaxy cluster number counts

The mass function of cluster-size halos and their redshift distribution are computed for 12 distinct accelerating cosmological scenarios and confronted to the predictions of the conventional flat Lambda CDM model. The comparison with Lambda CDM is performed by a two-step process. First, we determine the free parameters of all models through a joint analysis involving the latest cosmological data, using supernovae type Ia, the cosmic microwave background shift parameter, and baryon acoustic oscillations. Apart from a braneworld inspired cosmology, it is found that the derived Hubble relation of the remaining models reproduces the Lambda CDM results approximately with the same degree of statistical confidence. Second, in order to attempt to distinguish the different dark energy models from the expectations of Lambda CDM, we analyze the predicted cluster-size halo redshift distribution on the basis of two future cluster surveys: (i) an X-ray survey based on the eROSITA satellite, and (ii) a Sunayev-Zeldovich survey based on the South Pole Telescope. As a result, we find that the predictions of 8 out of 12 dark energy models can be clearly distinguished from the Lambda CDM cosmology, while the predictions of 4 models are statistically equivalent to those of the Lambda CDM model, as far as the expected cluster mass function and redshift distribution are concerned. The present analysis suggests that such a technique appears to be very competitive to independent tests probing the late time evolution of the Universe and the associated dark energy effects.

Generalized connectivity between any two nodes in a complex network

This article focuses on the identification of the number of paths with different lengths between pairs of nodes in complex networks and how these paths can be used for characterization of topological properties of theoretical and real-world complex networks. This analysis revealed that the number of paths can provide a better discrimination of network models than traditional network measurements. In addition, the analysis of real-world networks suggests that the long-range connectivity tends to be limited in these networks and may be strongly related to network growth and organization.

Rapid formation of isoprene photo-oxidation products observed in Amazonia

Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e. g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian Aerosol Characterization Experiment (AMAZE-08) we show that the production of certain OVOCs (e. g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. Recently reported fast secondary production could explain 50% of the observed discrepancy with the remaining part possibly produced via a novel primary production channel, which has been proposed theoretically. The observations of OVOCs are also used to test a recently proposed HO(x) recycling mechanism via degradation of isoprene peroxy radicals. If generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in uncertainties of modelled OH reactivity, potentially explaining a fraction of the missing OH sink over forests which has previously been largely attributed to a missing source of primary biogenic VOCs.

Nonlinear diffraction of light beams propagating in photorefractive media with embedded reflecting wire

The theory of nonlinear diffraction of intensive light beams propagating through photorefractive media is developed. Diffraction occurs on a reflecting wire embedded in the nonlinear medium at a relatively small angle with respect to the direction of the beam propagation. It is shown that this process is analogous to the generation of waves by a flow of a superfluid past an obstacle. The ""equation of state"" of such a superfluid is determined by the nonlinear properties of the medium. On the basis of this hydrodynamic analogy, the notion of the ""Mach number"" is introduced where the transverse component of the wave vector plays the role of the fluid velocity. It is found that the Mach cone separates two regions of the diffraction pattern: inside the Mach cone oblique dark solitons are generated and outside the Mach cone the region of ""optical ship waves"" (the wave pattern formed by a two-dimensional packet of linear waves) is situated. Analytical theory of the ""optical ship waves"" is developed and two-dimensional dark soliton solutions of the generalized two-dimensional nonlinear Schrodinger equation describing the light beam propagation are found. Stability of dark solitons with respect to their decay into vortices is studied and it is shown that they are stable for large enough values of the Mach number.

Generalized Sznajd model for opinion propagation

In the last decade the Sznajd model has been successfully employed in modeling some properties and scale features of both proportional and majority elections. We propose a version of the Sznajd model with a generalized bounded confidence rule-a rule that limits the convincing capability of agents and that is essential to allow coexistence of opinions in the stationary state. With an appropriate choice of parameters it can be reduced to previous models. We solved this model both in a mean-field approach (for an arbitrary number of opinions) and numerically in a Barabaacutesi-Albert network (for three and four opinions), studying the transient and the possible stationary states. We built the phase portrait for the special cases of three and four opinions, defining the attractors and their basins of attraction. Through this analysis, we were able to understand and explain discrepancies between mean-field and simulation results obtained in previous works for the usual Sznajd model with bounded confidence and three opinions. Both the dynamical system approach and our generalized bounded confidence rule are quite general and we think it can be useful to the understanding of other similar models.

Coexistence of interacting opinions in a generalized Sznajd model

The Sznajd model is a sociophysics model that mimics the propagation of opinions in a closed society, where the interactions favor groups of agreeing people. It is based in the Ising and Potts ferromagnetic models and, although the original model used only linear chains, it has since been adapted to general networks. This model has a very rich transient, which has been used to model several aspects of elections, but its stationary states are always consensus states. In order to model more complex behaviors, we have, in a recent work, introduced the idea of biases and prejudices to the Sznajd model by generalizing the bounded confidence rule, which is common to many continuous opinion models, to what we called confidence rules. In that work we have found that the mean field version of this model (corresponding to a complete network) allows for stationary states where noninteracting opinions survive, but never for the coexistence of interacting opinions. In the present work, we provide networks that allow for the coexistence of interacting opinions for certain confidence rules. Moreover, we show that the model does not become inactive; that is, the opinions keep changing, even in the stationary regime. This is an important result in the context of understanding how a rule that breeds local conformity is still able to sustain global diversity while avoiding a frozen stationary state. We also provide results that give some insights on how this behavior approaches the mean field behavior as the networks are changed.

Comparative study of the adsorption and dissociation of vinylacetic acid and acrylic acid on silicon (001)

In this work, we employ the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory, to investigate the adsorption process of acrylic acid (AAc) and vinylacetic acid (VAA) on the silicon surface. Our total energy calculations support the proposed experimental process, as it indicates that the chemisorption of the molecule is as follows: The gas phase VAA (AAc) adsorbs molecularly to the electrophilic surface Si atom and then dissociates into H(2)C = CH - COO and H, bonded to the electrophilic and nucleophilic surface silicon dimer atoms, respectively. The activation energy for both processes correspond to thermal activations that are smaller than the usual growth temperature. In addition, the electronic structure, calculated vibrational modes, and theoretical scanning tunneling microscopy images are discussed, with a view to contribute to further experimental investigations.

Nonempirical hyper-generalized-gradient functionals constructed from the Lieb-Oxford bound

A simple and completely general representation of the exact exchange-correlation functional of density-functional theory is derived from the universal Lieb-Oxford bound, which holds for any Coulomb-interacting system. This representation leads to an alternative point of view on popular hybrid functionals, providing a rationale for why they work and how they can be constructed. A similar representation of the exact correlation functional allows to construct fully nonempirical hyper-generalized-gradient approximations (HGGAs), radically departing from established paradigms of functional construction. Numerical tests of these HGGAs for atomic and molecular correlation energies and molecular atomization energies show that even simple HGGAs match or outperform state-of-the-art correlation functionals currently used in solid-state physics and quantum chemistry.