A moving mesh method for modelling defects in nematic liquid crystals

The properties of liquid crystals can be modelled using an order parameter which describes the variability of the local orientation of rod-like molecules. Defects in the director field can arise due to external factors such as applied electric or magnetic fields, or the constraining geometry of the cell containing the liquid crystal material. Understanding the formation and dynamics of defects is important in the design and control of liquid crystal devices, and poses significant challenges for numerical modelling. In this paper we consider the numerical solution of a Q-tensor model of a nematic liquid crystal, where defects arise through rapid changes in the Q-tensor over a very small physical region in relation to the dimensions of the liquid crystal device. The efficient solution of the resulting six coupled partial differential equations is achieved using a finite element based adaptive moving mesh approach, where an unstructured triangular mesh is adapted towards high activity regions, including those around defects. Spatial convergence studies are presented using a stationary defect as a model test case, and the adaptive method is shown to be optimally convergent using quadratic triangular finite elements. The full effectiveness of the method is then demonstrated using a challenging two-dimensional dynamic Pi-cell problem involving the creation, movement, and annihilation of defects

Vertebrate Reservoirs of Arboviruses : Myth, Synonym of Amplifier, or Reality?

The rapid succession of the pandemic of arbovirus diseases, such as dengue, West Nile fever, chikungunya, and Zika fever, has intensified research on these and other arbovirus diseases worldwide. Investigating the unique mode of vector-borne transmission requires a clear understanding of the roles of vertebrates. One major obstacle to this understanding is the ambiguity of the arbovirus definition originally established by the World Health Organization. The paucity of pertinent information on arbovirus transmission at the time contributed to the notion that vertebrates played the role of reservoir in the arbovirus transmission cycle. Because this notion is a salient feature of the arbovirus definition, it is important to reexamine its validity. This review addresses controversial issues concerning vertebrate reservoirs and their role in arbovirus persistence in nature, examines the genesis of the problem from a historical perspective, discusses various unresolved issues from multiple points of view, assesses the present status of the notion in light of current knowledge, and provides options for a solution to resolve the issue.Peer reviewe

Online interventions for problem gamblers with and without co-occurring mental health symptoms: protocol for a randomized controlled trial

BACKGROUND Comorbidity between problem gambling and depression or anxiety is common. Further, the treatment needs of people with co-occurring gambling and mental health symptoms may be different from those of problem gamblers who do not have a co-occurring mental health concern. The current randomized controlled trial (RCT) will evaluate whether there is a benefit to providing access to mental health Internet interventions (G + MH intervention) in addition to an Internet intervention for problem gambling (G-only intervention) in participants with gambling problems who do or do not have co-occurring mental health symptoms. METHODS Potential participants will be screened using an online survey to identify participants meeting criteria for problem gambling. As part of the baseline screening process, measures of current depression and anxiety will be assessed. Eligible participants agreeing (N = 280) to take part in the study will be randomized to one of two versions of an online intervention for gamblers – an intervention that just targets gambling issues (G-only) versus a website that contains interventions for depression and anxiety in addition to an intervention for gamblers (G + MH). It is predicted that problem gamblers who do not have co-occurring mental health symptoms will display no significant difference between intervention conditions at a six-month follow-up. However, for those with co-occurring mental health symptoms, it is predicted that participants receiving access to the G + MH website will display significantly reduced gambling outcomes at six-month follow-up as compared to those provided with G-only website. DISCUSSION The trial will produce information on the best means of providing online help to gamblers with and without co-occurring mental health symptoms.This research was funded by the Manitoba Gambling Research Program of Manitoba Liquor and Lotteries

Marital interaction theory: some implications for research

This project examines specific basic areas of marital interaction theory. Individual chapters are developed around the following themes: historical development of the theory of interaction; a theoretical discussion of selected concepts; personality as a determinant of interaction; communication in marriage; marital interaction patterns; methodology pertaining to research findings; and finally some implications for research which became apparent as this project developed. The project lays the conceptual groundwork for a series of empirical studies that will use the interactional approach as a theoretical base. The immediate purpose of this project therefore is to describe the important dimensions of the interactional approach as these pertain to marital interaction. Interaction is defined as a reciprocal relationship in which each person may produce effects upon the other. Here the essence of marriage is interaction; thus marital interaction is critical in its effect on the spouses and the continuity of the marriage. Some of the basic concepts of George Mead are described and it is suggested that they are essential elements of the interactional approach. The major assumptions of this approach are that a) human behavior cannot be derived or inferred from nonhuman forms, b) the social act is the primary analytic unit for an understanding of society and the personality, c) the human infant is potentially social, and d) the human being is actor as well as reactor. Personality is discussed as a determinant of the quality and quantity of marital interaction. The issue of personal competence is explored, particularly in respect to verbal ability. Communication, the process of influence, is defined for marital interaction and the consequent formation of patterns. Identification and classification of marital interaction patterns are limited to a description of selected examples from family research and the observations of clinicians. Patterns tend to be defined in psychological terms although communicative behavior is stressed. The absence of common criteria and terminology is noted. Description of dysfunctional patterns predominates. Two methods frequently used in recent studies of marital interaction are direct observation and analysis of reports from marital partners. It is suggested that a combination of these techniques could increase the quantity of information about marital interaction. Research questions focus on the problem of adult socialization, its implications for the establishment of marital interaction patterns, and the need to determine the relation between the interaction process and the functional or dysfunctional quality of the resultant pattern. An inseparable part of the aforementioned research areas is the function of communication. It is suggested that investigation of verbal communication might yield significant data for the understanding of the interaction process as it affects the personalities of the spouses and the formation of patterns

Dengue and climate change in Australia: predictions for the future should incorporate knowledge from the past

•Dengue transmission in Australia is currently restricted to Queensland, where the vector mosquito Aedes aegypti is established. Locally acquired infections have been reported only from urban areas in the north-east of the state, where the vector is most abundant. •Considerable attention has been drawn to the potential impact of climate change on dengue distribution within Australia, with projections for substantial rises in incidence and distribution associated with increasing temperatures. •However, historical data show that much of Australia has previously sustained both the vector mosquito and dengue viruses. Although current vector distribution is restricted to Queensland, the area inhabited by A. aegypti is larger than the disease-transmission areas, and is not restricted by temperature (or vector-control programs); thus, it is unlikely that rising temperatures alone will bring increased vector or virus distribution. •Factors likely to be important to dengue and vector distribution in the future include increased dengue activity in Asian and Pacific nations that would raise rates of virus importation by travellers, importation of vectors via international ports to regions without A. aegypti, higher rates of domestic collection and storage of water that would provide habitat in urban areas, and growing human populations in northern Australia. •Past and recent successful control initiatives in Australia lend support to the idea that well resourced and functioning surveillance programs, and effective public health intervention capabilities, are essential to counter threats from dengue and other mosquito-borne diseases. •Models projecting future activity of dengue (or other vector-borne disease) with climate change should carefully consider the local historical and contemporary data on the ecology and distribution of the vector and local virus transmission