Isotropic-nematic phase equilibria of polydisperse hard rods: The effect of fat tails in the length distribution

We study the phase behaviour of hard rods with length polydispersity, treated within a simplified version of the Onsager model. We give a detailed description of the unusual phase behaviour of the system when the rod length distribution has a "fat" (e.g. log-normal) tail up to some finite cutoff. The relatively large number of long rods in the system strongly influences the phase behaviour: the isotropic cloud curve, which defines the where a nematic phase first occurs as density is increased, exhibits a kink; at this point the properties of the coexisting nematic shadow phase change discontinuously. A narrow three-phase isotropic-nematic-nematic coexistence region exists near the kink in the cloud curve, even though the length distribution is unimodal. A theoretical derivation of the isotropic cloud curve and nematic shadow curve, in the limit of large cutoff, is also given. The two curves are shown to collapse onto each other in the limit. The coexisting isotropic and nematic phases are essentially identical, the only difference being that the nematic contains a larger number of the longest rods; the longer rods are also the only ones that show any significant nematic ordering. Numerical results for finite but large cutoff support the theoretical predictions for the asymptotic scaling of all quantities with the cutoff length.Comment: 21 pages, 13 figure

Simplified Onsager theory for isotropic-nematic phase equilibria of length polydisperse hard rods

Polydispersity is believed to have important effects on the formation of liquid crystal phases in suspensions of rod-like particles. To understand such effects, we analyse the phase behaviour of thin hard rods with length polydispersity. Our treatment is based on a simplified Onsager theory, obtained by truncating the series expansion of the angular dependence of the excluded volume. We describe the model and give the full phase equilibrium equations; these are then solved numerically using the moment free energy method which reduces the problem from one with an infinite number of conserved densities to one with a finite number of effective densities that are moments of the full density distribution. The method yields exactly the onset of nematic ordering. Beyond this, results are approximate but we show that they can be made essentially arbitrarily precise by adding adaptively chosen extra moments, while still avoiding the numerical complications of a direct solution of the full phase equilibrium conditions. We investigate in detail the phase behaviour of systems with three different length distributions: a (unimodal) Schulz distribution, a bidisperse distribution and a bimodal mixture of two Schulz distributions which interpolates between these two cases. A three-phase isotropic-nematic-nematic coexistence region is shown to exist for the bimodal and bidisperse length distributions if the ratio of long and short rod lengths is sufficiently large, but not for the unimodal one. We systematically explore the topology of the phase diagram as a function of the width of the length distribution and of the rod length ratio in the bidisperse and bimodal cases.Comment: 18 pages, 16 figure

Advanced solutions for quality-oriented multimedia broadcasting

Multimedia content is increasingly being delivered via different types of networks to viewers in a variety of locations and contexts using a variety of devices. The ubiquitous nature of multimedia services comes at a cost, however. The successful delivery of multimedia services will require overcoming numerous technological challenges many of which have a direct effect on the quality of the multimedia experience. For example, due to dynamically changing requirements and networking conditions, the delivery of multimedia content has traditionally adopted a best effort approach. However, this approach has often led to the end-user perceived quality of multimedia-based services being negatively affected. Yet the quality of multimedia content is a vital issue for the continued acceptance and proliferation of these services. Indeed, end-users are becoming increasingly quality-aware in their expectations of multimedia experience and demand an ever-widening spectrum of rich multimedia-based services. As a consequence, there is a continuous and extensive research effort, by both industry and academia, to find solutions for improving the quality of multimedia content delivered to the users; as well, international standards bodies, such as the International Telecommunication Union (ITU), are renewing their effort on the standardization of multimedia technologies. There are very different directions in which research has attempted to find solutions in order to improve the quality of the rich media content delivered over various network types. It is in this context that this special issue on broadcast multimedia quality of the IEEE Transactions on Broadcasting illustrates some of these avenues and presents some of the most significant research results obtained by various teams of researchers from many countries. This special issue provides an example, albeit inevitably limited, of the richness and breath of the current research on multimedia broadcasting services. The research i- - ssues addressed in this special issue include, among others, factors that influence user perceived quality, encoding-related quality assessment and control, transmission and coverage-based solutions and objective quality measurements

Sobre la formación de los conceptos geométricos y sobre el léxico geométrico

El léxico geométrico está relacionado con un criterio de equivalencia entre figuras -normalmente dado por un grupo de transformación (K1ein) -. Puede haber un conflicto entre el lenguaje ordinario, el léxico geométrico tradicional y el criterio de equivalencia que puede sugerir una situación específica. En este artículo analizamos los resultados de un conjunto de preguntas con el objetivo de descubrir los criterios de equivalencia elegidos por los alumnos de entre 9 y 11 años, y la influencia de su léxico. Hemos observado una influencia considerable de los criterios basados en el grupo de traducciones y en el grupo de homoteties y traducciones. También hemos observado la influencia de ((modelos estándar)) (es decir, figuras que aparecen normalmente en sus libros), y algunas dificultades de conceptualización

High-Voltage Energy Harvesting and Storage System for Internet of Things Indoor Application

On the path toward independence from fossil fuels, solar energy is the mostpromising solution, but it needs a robust and reliable storage system to face itsintrinsicfluctuations due to location, day cycle, and weather. The integrationbetween energy harvesting and storage (H&S) technologies is a must toward cleanenergy production, and it becomes even more appealing considering the possi-bility of producing electricity not only from direct sunlight but also from diffuselight and indoor illumination. Herein, a dye-sensitized solar module (DSSM)developed to harvest indoor illumination and directly store it into an electricaldouble-layer capacitor (EDLC) is presented. Five series-connected dye-sensitizedsolar cells are fabricated on the same substrate and the module is integrated with ahigh-voltage EDLC. The integrated device is characterized under indoor lightsources such as light emitting diodes andfluorescent lamps. The results show oneof the highest efficiencies ever reported for a high-voltage DSSM under indoorillumination (16.27%), the largest voltage window ever reported for an indoor H&Sdevice based on DSSM and EDLC—up to 3 V—and an overall photoelectricconversion and storage efficiency of 9.73% under indoor illumination

ESCAP Expert Article: Borderline personality disorder in adolescence: An expert research review with implications for clinical practice

Borderline personality disorder (BPD) has onset in adolescence, but is typically first diagnosed in young adulthood. This paper provides a narrative review of the current evidence on diagnosis, comorbidity, phenomenology and treatment of BPD in adolescence. Instruments available for diagnosis are reviewed and their strengths and limitations discussed. Having confirmed the robustness of the diagnosis and the potential for its reliable clinical assessment, we then explore current understandings of the mechanisms of the disorder and focus on neurobiological underpinnings and research on psychological mechanisms. Findings are accumulating to suggest that adolescent BPD has an underpinning biology that is similar in some ways to adult BPD but differs in some critical features. Evidence for interventions focuses on psychological therapies. Several encouraging research studies suggest that early effective treatment is possible. Treatment development has just begun, and while adolescent-specific interventions are still in the process of evolution, most existing therapies represent adaptations of adult models to this developmental phase. There is also a significant opportunity for prevention, albeit there are few data to date to support such initiatives. This review emphasizes that there can be no justification for failing to make an early diagnosis of this enduring and pervasive problem

Uma ferramenta para cadastro e visualização de metadados em Agricultura de Precisão utilizando GeoNetwork.

A Rede Agricultura de Precisão (RedeAP) consiste em um sistema que pode ser descrito como uma estratégia de gestão dos dados produzidos nas Unidades Piloto, e é fundamentalmente constituído de três componentes inter-relacionados entre si, sendo eles: Bancos de Dados, Política de Acesso e uso dos Dados, e Aplicação. O componente de Aplicação se trata de um Sistema de Informações Geográficas para a Web baseado no software livre i3Geo com o aplicativo de catalogação de dados geoespaciais GeoNetwork (QUEIROS et al., 2011). A adição de novos registros no catálogo do GeoNetwork pode ser feita utilizando o próprio editor de metadados ou pela ferramenta de importação dos dados no formato XML. Em ambos os casos, o usuário deve ser, no mínimo, registrado como editor no grupo correspondente. Contudo, o controle de usuários, perfis e níveis de acesso deve ser feito pelo próprio sistema RedeAP, utilizando, assim, o GeoNetwork somente para a visualização dos metadados catalogados. Baseado nesse contexto, surgiu a necessidade da criação de uma ferramenta que fizesse a catalogação dos metadados com o objetivo de mantê-los armazenados no banco de dados do sistema e também possibilitar sua visualização nos padrões de exibição do GeoNetwork