Mechanical Behavior of the Lamellar Structure in Semi-Crystalline Polymers

We have employed molecular dynamics simulations to study the behavior of virtual polymeric materials under an applied uniaxial tensile load. Through computer simulations, one can obtain experimentally inaccessible information about phenomena taking place at the molecular and microscopic levels. Not only can the global material response be monitored and characterized along time, but the response of macromolecular chains can be followed independently if desired. The computer-generated materials were created by emulating the step-wise polymerization, resulting in self-avoiding chains in 3D with controlled degree of orientation along a certain axis. These materials represent a simplified model of the lamellar structure of semi-crystalline polymers,being comprised of an amorphous region surrounded by two crystalline lamellar regions. For the simulations, a series of materials were created, varying i) the lamella thickness, ii) the amorphous region thickness, iii) the preferential chain orientation, and iv) the degree of packing of the amorphous region. Simulation results indicate that the lamella thickness has the strongest influence on the mechanical properties of the lamella-amorphous structure, which is in agreement with experimental data. The other morphological parameters also affect the mechanical response, but to a smaller degree. This research follows previous simulation work on the crack formation and propagation phenomena, deformation mechanisms at the nanoscale, and the influence of the loading conditions on the material response. Computer simulations can improve the fundamental understanding about the phenomena responsible for the behavior of polymeric materials, and will eventually lead to the design of knowledge-based materials with improved properties.

Modelling the Mechanical Behavior of Polymer-Based Nanocomposites

Molecular dynamics simulations were employed to analyze the mechanical properties of polymer-based nanocomposites with varying nanofiber network parameters. The study was focused on nanofiber aspect ratio, concentration and initial orientation. The reinforcing phase affects the behavior of the polymeric nanocomposite. Simulations have shown that the fiber concentration has a significant effect on the properties, with higher loadings resulting in higher stress levels and higher stiffness, matching the general behavior from experimental knowledge in this field. The results also indicate that, within the studied range, the observed effect of the aspect ratio and initial orientation is smaller than that of the concentration, and that these two parameters are interrelated.

Coupling Mechanical and Electrical Behavior in the Multi-scale Simulation of Polymer-based CNT Nanocomposites

A numeric model has been proposed to investigate the mechanical and electrical properties of a polymeric/carbon nanotube (CNT) composite material subjected to a deformation force. The reinforcing phase affects the behavior of the polymeric matrix and depends on the nanofiber aspect ratio and preferential orientation. The simulations show that the mechanical behavior of a computer generated material (CGM) depends on fiber length and initial orientation in the polymeric matrix. It is also shown how the conductivity of the polymer/CNT composite can be calculated for each time step of applied stress, effectively providing the ability to simulate and predict strain-dependent electrical behavior of CNT nanocomposites.

GUI Behavior from Source Code Analysis

When developing interactive applications, considering the correctness of graphical user interfaces (GUIs) code is essential. GUIs are critical components of today's software, and contemporary software tools do not provide enough support for ensuring GUIs' code quality. GUIsurfer, a GUI reverse engineering tool, enables evaluation of behavioral properties of user interfaces. It performs static analysis of GUI code, generating state machines that can help in the evaluation of interactive applications. This paper describes the design, software architecture, and the use of GUIsurfer through an example. The tool is easily re-targetable, and support is available to Java/Swing, and WxHaskell. The paper sets the ground for a generalization effort to consider rich internet applications. It explores the GWT web applications' user interface programming toolkit.

Modifying fish gelatin electrospun membranes for biomedical applications: cross- linking and swelling behavior

Development of suitable membranes is a fundamental requisite for tissue and biomedical engineering applications. This work presents fish gelatin random and aligned electrospun membranes cross-linked with glutaraldehyde (GA). It was observed that the fiber average diameter and the morphology is not influenced by the GA exposure time and presents fibers with an average diameter around 250 nm. Moreover, when the gelatin mats are immersed in a phosphate buffered saline solution (PBS), they can retain as much as 12 times its initial weight of solution almost instantaneously, but the material microstructure of the fiber mats changes from the characteristic fibrous to an almost spherical porous structure. Cross-linked gelatin electrospun fiber mats and films showed a water vapor permeability of 1.37 ± 0.02 and 0.13 ± 0.10 (g.mm)/(m2.h.kPa), respectively. Finally, the processing technique and cross-linking process does not inhibit MC-3T3-E1 cell adhesion. Preliminary cell culture results showed good cell adhesion and proliferation in the cross-linked random and aligned gelatin fiber mats.

Predicting the mechanical behavior of amorphous polymeric materials under strain through multi-scale simulation

Polymeric materials have become the reference material for high reliability and performance applications. However, their performance in service conditions is difficult to predict, due in large part to their inherent complex morphology, which leads to non-linear and anisotropic behavior, highly dependent on the thermomechanical environment under which it is processed. In this work, a multiscale approach is proposed to investigate the mechanical properties of polymeric-based material under strain. To achieve a better understanding of phenomena occurring at the smaller scales, the coupling of a finite element method (FEM) and molecular dynamics (MD) modeling, in an iterative procedure, was employed, enabling the prediction of the macroscopic constitutive response. As the mechanical response can be related to the local microstructure, which in turn depends on the nano-scale structure, this multiscale approach computes the stress-strain relationship at every analysis point of the macro-structure by detailed modeling of the underlying micro- and meso-scale deformation phenomena. The proposed multiscale approach can enable prediction of properties at the macroscale while taking into consideration phenomena that occur at the mesoscale, thus offering an increased potential accuracy compared to traditional methods.

Consumer behavior and profile in cross border tourism destinations

Tourism is a phenomenon that moves millions of people around the world, taking as a major driver of the global economy. Such relevance is reflected in the proliferation of studies in the overall area known as tourism, under various perspectives and backgrounds. In the light of such multitude of insights our study aims at gaining a deeper understanding of customer profiling and behavior in cross-border tourism destinations. Previous studies conducted in such contexts suggest that cross-border regions (CBRs) are an attractive and desirable idea, yet requiring further theoretical and empirical research. The new configuration of many CBRs calls for a debate on issues concerning its development, raising up important dimensions, such as, organization and planning of common tourism destinations. There is still a gap in the understanding of destination management in CBRs and the customer profile and motivations. Overall this research aims at attaining a deeper understanding of the profile and behavior of consumers in tourism settings, addressing the predisposition for the destination. The study addresses the following research question: “What factors influence customer behavior and attitudes in a CBRs tourism destination?” To address our question we will take an interdisciplinary perspective bringing together inputs from marketing, tourism and local economics. When addressing consumer behavior in tourism previous studies considered the following constructs: involvement, place attachment, satisfaction and destination loyalty. In order to establish the causal relationships in our theoretical model, we intend to develop a predominant quantitative design, yet we plan to conduct exploratory interviews. In the analysis and discussion of results, we intend to use Structural Equation Modeling. It will further allow understanding how the constructs in the research model relate to each other in the specified context. Results are also expected to have managerial implications. Consequently our results may assist decision makers in developing their local policies.

Assedio moral e assedio sexual: faces do poder perverso nas organizações

Este artigo analisa duas faces do poder perverso nas organizações modernas: o assédio moral e o sexual. No momento em que as empresas buscam uma orientação mais ética e a melhoria do ambiente de trabalho, a discussão desses temas se faz prioridade. O texto apresenta, ainda, resultados de pesquisas realizadas na França e no Brasil.

Influence of discount price announcements on consumer's behavior

The theoretical framework that underpins this research study is based on the Prospect Theory formulated by Kahneman and Tversky, and Thaler's Mental Accounting Theory. The research aims to evaluate the consumers' behavior when different patterns of discount are offered (in percentage and absolute value and for larger and smaller discounts). Two experiments were conducted to explore these patterns of behavior and the results that were obtained supported the view that the framing effect was a common occurrence. The patterns of choice of individuals in a sample were found to be different due to changes in the ways discounts were offered. This can be explained by the various ways of presenting discount rates that had an impact on the influence of purchase intentions, recommendations and quality perception.

A JOINT EXPERIMENTAL ANALYSIS OF INVESTOR BEHAVIOR IN IPO PRICING METHODS

This article jointly examines the differences of laboratory versions of the Dutch clock open auction, a sealed-bid auction to represent book building, and a two-stage sealed bid auction to proxy for the “competitive IPO”, a recent innovation used in a few European equity initial public offerings. We investigate pricing, seller allocation, and buyer welfare allocation efficiency and conclude that the book building emulation seems to be as price efficient as the Dutch auction, even after investor learning, whereas the competitive IPO is not price efficient, regardless of learning. The competitive IPO is the most seller allocative efficient method because it maximizes offer proceeds. The Dutch auction emerges as the most buyer welfare allocative efficient method. Underwriters are probably seeking pricing efficiency rather than seller or buyer welfare allocative efficiency and their discretionary pricing and allocation must be important since book building is prominent worldwide.

Actividad Sexual y Prácticas de Riesgo en una Muestra de Estudiantes Universitarios Galegos

La utilización del preservativo en las relaciones sexuales con penetración constituye la única medida preventiva eficaz para evitar la transmisión sexual del VIH y otras ETS. Incrementar su uso adecuado y sistemático es por tanto el objetivo de las campañas de prevención dirigidas a disminuir los riesgos en la actividad sexual, especialmente en los adolescentes y adultos jóvenes, dentro de los que se está experimentando el mayor incremento de contagio. El objetivo de este estudio es evaluar el nivel de uso del preservativo masculino e identificar los principales conocimientos y actitudes vinculados a su uso de una muestra de 389 alumnos/as, estudiantes universitarios de primer curso de la Universidad de Vigo, Campus de Ourense con una edad media de 19.04 años. Los resultados muestran que el uso sistemático del preservativo agrupa el 45% de los sujetos de la muestra y no se detectando diferencias significativas en función del sexo (t=,021 p=,816). La mayoría de las relaciones sexuales de los jóvenes de la muestra se mantienen dentro de relaciones afectivas, y el uso del preservativo como anticonceptivo hace que éste sea suplantado por la píldora a mayor estabilidad percibida de la relación. Se verifica que el mayor uso del preservativo está vinculado a su percepción de utilidad como anticonceptivo y a la creencia de que tranquilizan y dan seguridad en la relación sexual, por lo tanto, en creer que posibilitan tener relaciones sexuales sin riesgos. Por otro lado, al cuestionar a las dos funciones por separado se verifica que el mayor el porcentaje de sujetos que recurre a las métodos anticonceptivos como forma de evitar embarazos (31%) que el de los que hacen uso de los mismos como medio para evitar enfremedades de transmisión sexual (3,1%), diferencias que han de ser adecuadamente incorporadas en los programas de prevención para potenciar de uso del preservativo, ya que constiyue el único profiláctico útil para prevenir E.T.S.

Aspectos da Vida Sexual de Doentes com Espinha Bífida em Portugal

O tratamento multidisciplinar da espinha bífida resultou num considerável aumento do número de doentes a atingirem a idade adulta. A vida sexual de um doente com espinha bífida está afectada não só pelas limitações físicas inerentes à doença, mas também pelos impactos psicológico e social desta doença. Trata-se de um tema de proporções pouco conhecidas, particularmente na população portuguesa de doentes com espinha bífida, na qual julgamos nunca ter sido feito um estudo do género. Dos 497 doentes sócios da ASBIHP, 219 têm idades superiores a 15 anos. Destes, um total de 27 doentes disponibilizaram-se a participar neste estudo tendo para tal respondido a um questionário por eles distribuído. Resultados: Apesar de ter sido fornecido algum tipo de educação sexual a quase todos os doentes, a maioria gostaria de receber informação específica sobre espinha bífida. De todos os doentes que participaram neste estudo, apenas 33,3 % viviam um relacionamento íntimo actual, apenas 22,2 % tiveram actividade sexual no último ano e apenas 25,9 % estavam satisfeitos com a sua actividade sexual actual. Incontinência e falta de auto-confiança foram considerados obstáculos importantes. Quando relacionados os vários factores conclui-se que os doentes jovens, de sexo masculino, com deambulação limitada a cadeira de rodas, mau controlo da incontinência urinária e fecal e com necessidade de utilização de fraldas ou pensos tiveram maiores dificuldades em estabelecer relacionamentos íntimos e em ter uma vida sexual activa e satisfatória. Conclusões: A sexualidade é importante para os doentes com espinha bífida. A educação sexual e a vigilância das dificuldades que estes doentes têm em atingir uma vida sexual activa e satisfatória, devem fazer parte dos objectivos dos profissionais de saúde que assistem estes doentes.

Reported Use of Anabolic Steroids and Ergogenic Substances in Gym/Health Club Settings: Associations with Psychosocial and Exercise Behavior Factors

The industry of ergogenic supplements is increasing rapidly (Cole et al., 2003). Supplements may constitute an important aid for some vigourous exercise routines, but they may also be used as a hypothetical mean to achieve increases in muscular mass. This supposed effect of suplements can lead to its use by individuals who have high levels of drive for muscularity, a condition that is known to be associated with muscular dismorphy (or as it has been called recently vigorexia, Pope et al., 1997). Another psychological factor which can influence supplement consumption is exercise dependence, a borderline problem, as most studies present a prevalence of less than 10% in regular exercisers (Palmeira & Matos, 2006). Symptoms like tolerance or continuity could lead to the use of ergogenic aids to maintain the exercise levels. Also of interest for the understanding of the use of suplements are exercise frequency, volume and intensity, which could explain the ratesof consumption on a more physicological level.

Infidelidade e ciúme no relacionamento amoroso e sexual

RESUMO: O presente estudo tem como objectivo avaliar a relação, por género, entre a infidelidade, o ciúme e a satisfação sexual. Para tal foi utilizada uma amostra de 186 sujeitos, de ambos os sexos, que preencheram um protocolo que incluía como medidas de avaliação um questionário de dados demográficos,um de envolvimentos românticos e sexuais, um de reacções emocionais à infidelidade do parceiro, o Multidimensional Jealousy Scale (Pfeiffer & Wong, 1989), o Big Five Inventory (Benet-Martinez & Oliver, 1998) e o Index Sexual Satisfaction (Hudson, Harrison & Crosscup, 1981). Foram encontradas diferenças entre géneros face à infidelidade, sendo que os homens consideram pior uma infidelidade sexual e as mulheres uma infidelidade emocional. A insatisfação sexual associou-se positivamente ao ciúme, em ambos os sexos, contudo, nas mulheres associou-se positivamente a duas dimensões do ciúme enquanto nos homens apenas se associou a uma. O ciúme associou-se de forma positiva com alguns sentimentos como traição, engano, ódio, rejeição ou desilusão, face à infidelidade, em ambos os sexos, o que parece indicar que ambos os sexos reagem aos dois tipos de infidelidade, contudo diferenciam-se na experiência dos sentimentos a ela associados. ABSTRACT: This study aims to assess the relationship, by gender, between infidelity, jealousy and sexual satisfaction. To this end it was used a sample of 186 individuals of both sexes, who completed a protocol that included evaluating measures such as one questionnaire assessing demographic data, one of sexual and romantic entanglements, and another one of emotional reactions to infidelity of the partner, Multidimensional Jealousy Scale (Pfeiffer & Wong,1989), the Big Five Inventory (Benet-Martinez & Oliver, 1998) and Sexual Satisfaction Index (Hudson, Harrison & Crosscup, 1981). Gender differences were found in relation to infidelity, while men consider worse sexual infidelity, women consider it emotional infidelity. Sexual dissatisfaction was positively associated with jealousy in both sexes, however, in women it was positively associated with the two dimensions of jealousy while in men it was associated with only one. Jealousy was associated positively with some feelings of betrayal, deceit, hate, rejection or disappointment towards infidelity for both sexes, suggesting that both sexes respond to the two types of infidelity, however they differ when experiencing feelings associated with it.