Coherent phonon transport in short-period two-dimensional superlattices of graphene and boron nitride

Promoting coherent transport of phonons at material interfaces is a promising strategy for controlling thermal transport in nanostructures and an alternative to traditional methods based on structural defects. Coherent transport is particularly relevant in short-period heterostructures with smooth interfaces and long-wavelength heat-carrying phonons, such as two-dimensional superlattices of graphene and boron nitride. In this work, we predict phonon properties and thermal conductivities in these superlattices using a normal mode decomposition approach. We study the variation of the frequency dependence of these properties with the periodicity and interface configuration (zigzag and armchair) for superlattices with period lengths within the coherent regime. Our results showed that the thermal conductivity decreases significantly from the first period length (0.44 nm) to the second period length (0.87 nm), 13% across the interfaces and 16% along the interfaces. For greater periods, the conductivity across the interfaces continues decreasing at a smaller rate of 11 W/mK per period length increase (0.43 nm), driven by changes in the phonon group velocities (coherent effects). In contrast, the conductivity along the interfaces slightly recovers at a rate of 2 W/mK per period, driven by changes in the phonon relaxation times (diffusive effects). By changing the interface configuration from armchair to zigzag, the conductivities for all period lengths increase by approximately 7% across the interfaces and 19% along the interfaces

Gyne and drone production in bombus atratus (Hymenoptera: Apidae)

For over a decade, our research group has studied the biology of the native bumblebee, Bombus atratus, to investigate the feasibility of using it to pollinate crops such as tomato, strawberry, blackberry and peppers. Traditionally, captive breeding has depended on the use of captured wild queens to initiate the colonies. The goal of the current work is to investigate conditions required to produce new queens and drones in captivity. In this study, 31 colonies were evaluated under either greenhouse or open field conditions over a 15 month period. A total of 1492 drones (D) and 737 gynes (G, i.e., virgin queens) were produced by all colonies, with 16 colonies producing both drones and gynes (D&G), 11 producing only drones (D) and 4 producing neither. Some of the D&G colonies had more than one sexual phase, but no colonies produced exclusively gynes. More drones and fewer gynes were produced per colony under greenhouse conditions with the highest number of drones produced by D&G colonies. The numbers of immature stages per cell declined in colonies as increasingly more resources were allocated to the production of gynes and the maintenance of increased nest temperature

Wetting of Nematic Liquid Crystals on Crenellated Substrates: A Frank–Oseen Approach

We revisit the wetting of nematic liquid crystals in contact with crenellated substrates, studied previously using the Landau–de Gennes formalism. However, due to computational limitations, the characteristic length scales of the substrate relief considered in that study limited to less than 100 nematic correlation lengths. The current work uses an extended Frank–Oseen formalism, which includes not only the free-energy contribution due to the elastic deformations but also the surface tension contributions and, if disclinations or other orientational field singularities are present, their core contributions. Within this framework, which was successfully applied to the anchoring transitions of a nematic liquid crystal in contact with structured substrates, we extended the study to much larger length scales including the macroscopic scale. In particular, we analyzed the interfacial states and the transitions between them at the nematic–isotropic coexistence

God\u27s Mercy and Justice in the Context of the Cosmic Conflict

Problem When it comes to the right balance concerning God’s character of mercy and justice in relation to His dealings with sin in its different manifestations, a number of theologians, as well as Christians in general, have struggled to harmonize the existence of these two attributes in all God’s actions toward sinners. This difficulty has led many to think of divine mercy and justice as attributes that cannot fit together in what is called the cosmic conflict between good and evil. This, therefore, demands a theological study based on Scripture as a whole to draw solid findings in response to the problems related to God’s character of mercy and justice in the unfolding of this cosmic conflict. Method This research will first provide a survey of how divine mercy and justice have been handled by some theologians and philosophers, in general, throughout Christian history, plus an overview of how the problem of the existence of “evil” in opposition to God has been seen by recent and contemporary theologians. Next, it will bring a presentation of Hebrew and Greek terminologies related to the theme. In addition, an analysis of texts in which God is concomitantly stated as being merciful and just will be employed, also providing a brief presentation of other texts where God is exclusively declared to be either merciful or just. The topic will then be evaluated through major events in the unfolding of the interplay between good and evil as a metanarrative in Scripture. Finally, the ramifications of the research will establish some concepts for theological topics and Christian ethics. Results By way of a systematic approach performed in this study, the biblical witness is coherent, for it points to a reality in which God has, indeed, acted mercifully and justly with His creatures in all circumstances since sin entered into this world, thus giving origin to what is called a cosmic conflict between good and evil. Conclusion Scripture responds to the difficulty in harmonizing divine mercy and justice by showing that in all His actions amid this spiritual warfare, God has revealed these two attributes of His character. They are always present and united as representative of His love in saving humankind

Undergraduate geotechnical engineering education of the 21st century

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal.Peer ReviewedPostprint (author's final draft

Pattern-induced anchoring transitions in nematic liquid crystals

In this paper we revisit the problem of a nematic liquid crystal in contact with patterned substrates. The substrate is modelled as a periodic array of parallel infinite grooves of well-defined cross section sculpted on a chemically homogeneous substrate which favors local homeotropic anchoring of the nematic. We consider three cases: a sawtooth, a crenellated and a sinusoidal substrate. We analyse this problem within the modified Frank-Oseen formalism. We argue that, for substrate periodicities much larger than the extrapolation length, the existence of different nematic textures with distinct far-field orientations, as well as the anchoring transitions between them, are associated with the presence of topological defects either on or close to the substrate. For the sawtooth and sinusoidal case, we observe a homeotropic to planar anchoring transition as the substrate roughness is increased. On the other hand, a homeotropic to oblique anchoring transition is observed for crenellated substrates. In this case, the anchoring phase diagram shows a complex dependence on the substrate roughness and substrate anchoring strength.Comment: 36 pages, 15 figures, revised version submitted to Journal of Physics: Condensed Matte

TICE : factor de mudança na organização educativa? Um estudo de caso sobre a integração das TICE numa escola Nónio

Citação bibliográfica: Gonçalves, Zita & SILVA, Bento (2003). TICE – factor de mudança na organização educativa?: Um estudo de caso sobre a integração das TICE numa Escola Nónio. In Paulo Dias & Varela de Freitas (orgs.), Actas do III Congresso Internacional de Tecnologias de Informação e Comunicação na Educação, Challenges 2003. Braga: Centro de Competência da Universidade do Minho, pp. 427-434. (ISBN: 972-8746-13-X)Respondendo à necessidade de renovação e adaptação das escolas Portuguesas aos desafios da Sociedade de Informação e Conheciment o, tem-se vindo a assistir à constante e progressiva integração das Tecnologias de Informação e Comunicação na Educação (TICE) e na Escola através da execução de diversos programas e projectos. Um deles, o "Programa Nónio – Século XXI", emanado do ME, foi responsável pelos projectos criados em inúmeras escolas abrangendo desde o pré-escolar até ao nível secundário. Esta comunicação aborda os principais factores impulsionadores e os condicionantes da desejada integração das TICE, quer os adiantados pela literatura neste domínio, quer os encontrados numa investigação levada a cabo recentemente. A investigação efectuada teve como objectivo avaliar que mudanças educativas se tinham operado pela integração das TICE numa "escola Nónio" abrangida pelo Centro de Competência Nónio da Universidade do Minho. Recorrendo à metodologia de estudo de caso, acompanhámos e monitorámos o desenvolvimento do projecto em TICE, desta escola, durante os seus três anos de vida. Para tal utilizámos, sobretudo, uma diversidade de métod os e técnicas de investigação de natureza qualitativa (observação, diários, registos, entrevistas, consulta de relatórios escolares). A terminar, chamamos a atenção para o riquíssimo papel das TICE não só na aprendizagem como no processo a autonomização do aluno pelo facto de promover a formação de "comunidades colaborativas de aprendizagem"

Construção de um instrumento de avaliação da integração das TIC na Escola

A integração das Tecnologias de Informação e Comunicação (TIC) na Educação e na Escola tem sido levada a efeito através da execução de vários programas e projectos. No caso Português, o Programa Nónio - Século XXI constitui hoje em dia uma das principais iniciativas lançadas pelo Ministério da Educação, pretendendo responder à necessidade de adaptar as escolas às novas exigências colocadas pela sociedade da informação. As escolas candidatam-se apresentando projectos de aplicação das TIC, os quais são devidamente acompanhados por Centros de Competência do Programa Nónio. No desenvolvimento de um projecto, a avaliação constitui um dos momentos chave. Considerando-se que se trata do processo pelo qual se delimitam, obtêm e fornecem informações úteis que permitem julgar sobre decisões possíveis, a avaliação deve ser posta ao serviço de uma melhor gestão da acção. Esta comunicação trata da concepção de um questionário para avaliar a integração das TIC na Escola. Tendo por base o instrumento “Indicadores de Qualidade do Uso das TIC em Educação” elaborado pela NAACE (National Association of Advisers for Computers in Education), construímos e validámos para a realidade portuguesa um questionário, especialmente aconselhado para recolha de dados junto de populações e amostras alargadas, permitindo obter informação sobre os padrões de competência, as condições de ensino e a administração das TIC