Methane Clathrates in the Solar System

We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate layers may exist on Pluto as well. Key Words: Methane clathrate-Protosolar nebula-Terrestrial planets-Outer Solar System.

The sources of inequity in the education system of Serbia and how to combat them

The concept of equal opportunity for all students is deeply embedded in the Serbian constitution and in education laws. On that level, there is no doubt that everyone is ensured an opportunity to receive quality education. Many measures in education policy have been created specifically to achieve this objective and make the system fair and inclusive. The Coleman Report was linked to a wave of optimism that certain educational measures would help in achieving these noble goals. This aim is a high priority in education in a democratic country, and due to its importance needs to be re-examined. Thus, the present research examines the equity of students in the Serbian education system, detecting areas on all educational levels that could be (or already are) systemic sources of inequity (e.g., criteria for preschool institution enrolment, the system of student awards, rationalisation of the school network, the concept of entrance exams to secondary school or university, etc.). A number of measures have already been taken in the system specifically to deal with inequity (e.g., the Preschool Preparatory Programme, dropout measures, inclusion, scholarships, etc.). The effects of these measures in particular are analysed in the present work. In addition to an analysis of the systemic sources of inequity in the Serbian education system, the article also makes recommendations for their overcoming. (DIPF/Orig.)

Bananas adrift in time – a case study in the Solomons

Diseases, pests and environmental constraints pose a major threat to the sustainability of banana production globally. To address these challenges, the discovery and study of new sources of genetic resistance and adaptability are required, along with the general conservation of diversity. The Solomon Islands, located in the south-western Pacific region near Papua New Guinea, are a major center of banana diversity. Some collections had been made by nationals of some of the diversity present but little was known internationally of the rich genetic resource present. Two separate visits to the Solomon Islands characterized banana collections, documented and collected germplasm, recommended conservation strategies and provided training in cultivar characterization. A remarkable range of genetic diversity was found, including: many AA and AAA cooking types somewhat like those present in Papua New Guinea; nine Fei cultivars in relatively common usage, and two undescribed wild species as well as five AAB Pacific Plantains and four ABB cooking bananas belonging to the Kalapua subgroup. About six of the unique cultivars were successfully collected and established in the regional in vitro germplasm collection of SPC in Suva, Fiji. Nine Solomon Islanders were trained in the finer points of characterizing banana cultivars. Further collecting and study/evaluation of this rich diversity will promote its appreciation and potential utilization for meeting the challenges and opportunities ahead. Future studies could also determine the spread of the Awawe species and variability of morphological traits in the population. Community-based conservation could promote awareness of dietary diversity for better nutrition, via using the Fei bananas described in this paper. Establishing a virus-free regional field collection could help in comprehensively characterizing and evaluating regional Musa genetic resources. Existing sites could embrace the broader unique diversity of the Solomon Islands, and facilitate sharing this diversity in conjunction with a regional virus-tested in vitro collection.

Utilising presence in places to support mobile interaction

Physical places are given contextual meaning by the objects and people that make up the space. Presence in physical places can be utilised to support mobile interaction by making access to media and notifications on a smartphone easier and more visible to other people. Smartphone interfaces can be extended into the physical world in a meaningful way by anchoring digital content to artefacts, and interactions situated around physical artefacts can provide contextual meaning to private manipulations with a mobile device. Additionally, places themselves are designed to support a set of tasks, and the logical structure of places can be used to organise content on the smartphone. Menus that adapt the functionality of a smartphone can support the user by presenting the tools most likely to be needed just-in-time, so that information needs can be satisfied quickly and with little cognitive effort. Furthermore, places are often shared with people whom the user knows, and the smartphone can facilitate social situations by providing access to content that stimulates conversation. However, the smartphone can disrupt a collaborative environment, by alerting the user with unimportant notifications, or sucking the user in to the digital world with attractive content that is only shown on a private screen. Sharing smartphone content on a situated display creates an inclusive and unobtrusive user experience, and can increase focus on a primary task by allowing content to be read at a glance. Mobile interaction situated around artefacts of personal places is investigated as a way to support users to access content from their smartphone while managing their physical presence. A menu that adapts to personal places is evaluated to reduce the time and effort of app navigation, and coordinating smartphone content on a situated display is found to support social engagement and the negotiation of notifications. Improving the sensing of smartphone users in places is a challenge that is out-with the scope of this thesis. Instead, interaction designers and developers should be provided with low-cost positioning tools that utilise presence in places, and enable quantitative and qualitative data to be collected in user evaluations. Two lightweight positioning tools are developed with the low-cost sensors that are currently available: The Microsoft Kinect depth sensor allows movements of a smartphone user to be tracked in a limited area of a place, and Bluetooth beacons enable the larger context of a place to be detected. Positioning experiments with each sensor are performed to highlight the capabilities and limitations of current sensing techniques for designing interactions with a smartphone. Both tools enable prototypes to be built with a rapid prototyping approach, and mobile interactions can be tested with more advanced sensing techniques as they become available. Sensing technologies are becoming pervasive, and it will soon be possible to perform reliable place detection in-the-wild. Novel interactions that utilise presence in places can support smartphone users by making access to useful functionality easy and more visible to the people who matter most in everyday life.