Bent surface free energy differences from simulation

We present a calculation of the change of free energy of a solid surface upon bending of the solid. It is based on extracting the surface stress through a molecular dynamics simulation of a bent slab by using a generalized stress theorem formula, and subsequent integration of the stress with respect to strain as a function of bending curvature. The method is exemplified by obtaining and comparing free energy changes with curvature of various reconstructed Au(001) surfaces.Comment: 14 pages, 2 figures, accepted for publication in Surface Science (ECOSS-19

A responsive client architecture with local object behavior deployment

Information Systems with a large user base require thin client technology due to deployment issues. Configuration and version management, added to maintenance cost are major players on this decision. However, heavy traffic loads and network latency impose severe penalties on users. A candidate solution to this problem must optimize users ergonomics whilst keeping maintenance costs low. In a straightforward approach, client architectures should provide web deployable local processing facilities. This paper describes an architecture based on the MVC paradigm capable of porting portions of the system to client executable scripts. Required entities are encapsulated in XML carriers and exchanged on demand between client and server side systems. Numerous user interactions are executed on the client side, relieving the network and improving responsivity. This solution not only enhances ergonomics but is also highly scalabled, delegating tasks to the greater number of client machines, whereas focusing server activity on more relevant operations

Explorando a robustez de servidores enterprise JavaBeans

ln the last years the growth of lava technology created a promising market: the application server market. The growing number of products being offered brings the need of a deep analysis of these products in order to guarantee that they can cover all the requirements of a system. This paper discusses a few metrics that can be used in order to evaluate the performance of application servers that implement the Enterprise JavaBeans specification, and shows some tests that can be used to generate concrete conclusions about the performance and viability of an application server.Nos últimos anos o crescimento da tecnologia lava criou um mercado bastante promissor: o de servidores de aplicação. Com o aumento da oferta de produtos nesse mercado toma-se necessária uma avaliação profunda sobre um produto para se garantir que o mesmo cumpra os requisitos de um sistema. Este trabalho procura levantar métricas que possam ser usadas com o objetivo de avaliar a performance de servidores que implementam a especificação Enterprise JavaBeans, e a partir dessas métricas gerar baterias de testes que possam gerar conclusões concretas sobre a performance e a viabilidade de um servidor

Theoretical study of Ga-based nanowires and the interaction of Ga with single-wall carbon nanotubes

Gallium displays physical properties which can make it a potential element to produce metallic nanowires and high-conducting interconnects in nanoelectronics. Using first-principles pseudopotential plane method we showed that Ga can form stable metallic linear and zigzag monatomic chain structures. The interaction between individual Ga atom and single-wall carbon nanotube (SWNT) leads to a chemisorption bond involving charge transfer. Doping of SWNT with Ga atom gives rise to donor states. Owing to a significant interaction between individual Ga atom and SWNT, continuous Ga coverage of the tube can be achieved. Ga nanowires produced by the coating of carbon nanotube templates are found to be stable and high conducting.Comment: 8 pages, 8 figure

Tachyon Vacuum Solution in Open String Field Theory with Constant B Field

We show that Schnabl's tachyon vacuum solution is an exact solution of the equation of motion of Witten's open bosonic string field theory in the background of constant antisymmetric two-form field. The action computed at the vacuum solution is given by the Dirac-Born-Infeld factor multiplied to that without the antisymmetric tensor field.Comment: 8 page

Electronic Properties of Ultra-Thin Aluminum Nanowires

We have carried out first principles electronic structure and total energy calculations for a series of ultrathin aluminum nanowires, based on structures obtained by relaxing the model wires of Gulseren et al. The number of conducting channels is followed as the wires radius is increased. The results suggest that pentagonal wires should be detectable, as the only ones who can yield a channel number between 8 and 10.Comment: 9 pages + 3 figures, to appear on Surface Scienc

Magic structures of helical multi-shell zirconium nanowires

The structures of free-standing zirconium nanowires with 0.6$-$2.8 nm in diameter are systematically studied by using genetic algorithm simulations with a tight-binding many body potential. Several multi-shell growth sequences with cylindrical structures are obtained. These multi-shell structures are composed of coaxial atomic shells with the three- and four-strands helical, centered pentagonal and hexagonal, and parallel double-chain-core curved surface epitaxy. Under the same growth sequence, the numbers of atomic strands in inner- and outer-shell show even-odd coupling and usually differ by five. The size and structure dependence of angular correlation functions and vibrational properties of zirconium nanowire are also discussed.Comment: 14 pages, 4 figure

Jogos eletrônicos educativos: um estudo de caso

The repetitive explanation of a subject through long communications and exercises are dull, turning study into a tedious chore. Moreover, not with standing subjects explained the purpose of learning them is not clearly stated. Students do not manage to relate the real interest and the individual interest. The elusive purpose diminishes the motivation of the student impairing the learning. It is necessary to create challenges so that student becomes motivated and can acquire knowledge. The use of ludic activities, which serves as an instrument interconnecting the student to the studied subject, can improve the learning process. This article considers the use of an educative game to motivate the student. The game amuses the student and increases the possibilities of learning concepts conveyed by the game. The student learns playing because the acquired knowledge is the key for his success.A explicação de um assunto através de explanações longas e exercícios repetitivos são maçantes, tornando o estudo tedioso. Além disso, os assuntos são explicados mas o propósito do aprendizado não fica claro para o aluno. Os alunos não conseguem relacionar o interesse real e o interesse individual. A falta de propósito diminui a motivação do aluno dificultando o aprendizado. É necessário criar desafios para que o aluno se sinta motivado e seja capaz de adquirir o conhecimento desejado.A utilização de atividades lúdicas, que sirvam como um instrumento que permita a interconexão entre o aluno e o assunto estudado, pode melhorar o processo de aprendizagem. Este artigo1 propõe a utilização de um jogo eletrônico educativo para motivar o aluno. O jogo diverte o aluno e aumenta as chances de aprendizagem de conceitos inseridos no jogo. O aluno aprende brincando porque o conhecimento adquirido é a chave do sucesso no jogo

The Puzzling Stability of Monatomic Gold Wires

We have examined theoretically the spontaneous thinning process of tip-suspended nanowires, and subsequently studied the structure and stability of the monatomic gold wires recently observed by Transmission Electron Microscopy (TEM). The methods used include thermodynamics, classical many-body force simulations, Local Density (LDA) and Generalized Gradient (GGA) electronic structure calculations as well as ab-initio simulations including the two tips. The wire thinning is well explained in terms of a thermodynamic tip suction driving migration of surface atoms from the wire to the tips. For the same reason the monatomic wire becomes progressively stretched. Surprisingly, however, all calculations so far indicate that the stretched monatomic gold wire should be unstable against breaking, contrary to the apparent experimental stability. The possible reasons for the observed stability are discussed.Comment: 4 figure

Genome sequencing and transcriptome analyses of the Siberian hamster hypothalamus identify mechanisms for seasonal energy balance

Synthesis of triiodothyronine (T3) in the hypothalamus induces marked seasonal neuromorphology changes across taxa. How species-specific responses to T3 signaling in the CNS drive annual changes in body weight and energy balance remains uncharacterized. These experiments sequenced and annotated the Siberian hamster (Phodopus sungorus) genome, a model organism for seasonal physiology research, to facilitate the dissection of T3-dependent molecular mechanisms that govern predictable, robust, and long-term changes in body weight. Examination of the Phodopus genome, in combination with transcriptome sequencing of the hamster diencephalon under winter and summer conditions, and in vivo-targeted expression analyses confirmed that proopiomelanocortin (pomc) is a primary genomic target for the long-term T3-dependent regulation of body weight. Further in silico analyses of pomc promoter sequences revealed that thyroid hormone receptor 1β-binding motif insertions have evolved in several genera of the Cricetidae family of rodents. Finally, experimental manipulation of food availability confirmed that hypothalamic pomc mRNA expression is dependent on longer-term photoperiod cues and is unresponsive to acute, short-term food availability. These observations suggest that species-specific responses to hypothalamic T3, driven in part by the receptor-binding motif insertions in some cricetid genomes, contribute critically to the long-term regulation of energy balance and the underlying physiological and behavioral adaptations associated with the seasonal organization of behavior. © 2019 National Academy of Sciences. All rights reserved