Highly sensitive multichannel spectrometer for subpicosecond spectroscopy in the midinfrared

A spectrometer system is presented for time-resolved probing in the midinfrared between 5 and 11 /tLmw ith a temporal resolution of better than 400 fs. Multichannel detection with HgCdTe detector arrays consisting of ten elements in combination with a high repetition rate permits one to record weak absorbance changes with an accuracy of 0.1 mOD

A Talk on the Wild Side: The Direct and Indirect Impact of Speech Recognition on Learning Gains

Research in the learning sciences and mathematics education has suggested that ‘thinking aloud’ (verbalization) can be important for learning. In a technology-mediated learning environment, speech might also help to promote learning by enabling the system to infer the students’ cognitive and affective state so that they can be provided a sequence of tasks and formative feedback, both of which are adapted to their needs. For these and associated reasons, we developed the iTalk2Learn platform that includes speech production and speech recognition for children learning about fractions. We investigated the impact of iTalk2Learn’s speech functionality in classrooms in the UK and Germany, with our results indicating that a speech-enabled learning environment has the potential to enhance student learning gains and engagement, both directly and indirectly

Plurality of hubs and emerging place typologies in Gulf cities

Rulers of Gulf countries have developed a strong interest in establishing and promoting new visions of their capital and major cities over the past few decades. In particular, the new vision to establish hubs in various economic sectors including trade, transit and tourism as well as culture and education have instigated a variety of mega projects and subsequently a diversity of place typologies. This paper explores newly emerging places and their networks rooted in distinctive hub visions, which have resulted in globalised urban spaces as nodal points within international networks

Perceiving urban liveability in an emerging migrant city

Gulf cities have witnessed rapid urban growth where new migrant communities from various cultural backgrounds have been evolving over the last two decades. This paper explores perceptions of liveable urban environments in Qatar's capital city, Doha. An attitude survey of 280 migrant professionals from different cultural backgrounds engaged in the high service sector was conducted. A profile for each cultural group including westerners, middle easterners, Indians and Southeast Asians was developed to analyse the way in which the key liveability factors are perceived. Factors were classified into two overarching categories: urban life and urban spaces. Urban life category included aspects that pertain to traffic and movement experience, residential satisfaction, shopping experience, and satisfaction regarding leisure and service spaces. Urban space category included attractiveness, iconicity and familiarity, which were attitudinally explored in four public open spaces. The inquiry has uncovered a number of concerns related to traffic experience, housing quality, parking spaces, school facilities and shopping opportunities. This may stymie the city's global attractiveness success on the global stage while warranting the need for addressing liveability as a part of future development plans

Crossover between distinct mechanisms of microwave photoresistance in bilayer systems

We report on temperature-dependent magnetoresistance measurements in balanced double quantum wells exposed to microwave irradiation for various frequencies. We have found that the resistance oscillations are described by the microwave-induced modification of electron distribution function limited by inelastic scattering (inelastic mechanism), up to a temperature of T*~4 K. With increasing temperature, a strong deviation of the oscillation amplitudes from the behavior predicted by this mechanism is observed, presumably indicating a crossover to another mechanism of microwave photoresistance, with similar frequency dependence. Our analysis shows that this deviation cannot be fully understood in terms of contribution from the mechanisms discussed in theory.Comment: 7 pages, 4 figure

Coexistence of bulk and surface states probed by Shubnikov-de Haas oscillations in Bi2_2Se3_3 with high charge-carrier density

Topological insulators are ideally represented as having an insulating bulk with topologically protected, spin-textured surface states. However, it is increasingly becoming clear that these surface transport channels can be accompanied by a finite conducting bulk, as well as additional topologically trivial surface states. To investigate these parallel conduction transport channels, we studied Shubnikov-de Haas oscillations in Bi$_2$Se$_3$ thin films, in high magnetic fields up to 30 T so as to access channels with a lower mobility. We identify a clear Zeeman-split bulk contribution to the oscillations from a comparison between the charge-carrier densities extracted from the magnetoresistance and the oscillations. Furthermore, our analyses indicate the presence of a two-dimensional state and signatures of additional states the origin of which cannot be conclusively determined. Our findings underpin the necessity of theoretical studies on the origin of and the interplay between these parallel conduction channels for a careful analysis of the material's performance.Comment: Manuscript including supplemental materia

Socio-spatial practice of migrant communities in Doha's traditional core : the case of Al Asmakh district

This paper is based on an extensive research undertaken at Qatar University in 2014 with the aim of exploring the social-spatial practice of migrant communities in Doha’s traditional core. Since new development strategies have been initiated in Gulf cities, the old historic centres have faced a rapid transformation process. Today, large scale investments in new developments in Doha’s traditional centre have led to a new challenge to prevent the complete social restructuring and the move of all residing migrant communities, particularly those who have settled in Doha for generations, from the centre to other newly urbanized areas. While large-scale projects, such as Msheireb regeneration and redevelopment, have led to the replacement of an entire district, there have been fragmented development initiatives to gradually upgrade existing urban structures in central areas. The district of the Al Asmakh is one of the most important examples that manifest the current conflict to mediate between rising investment pressures and preserving the local identity including the particular urban life and spatial economic settings, which have evolved over several decades. The paper presents new research outcomes with respect to the lived urban spaces of the Al Asmakh in order to illustrate the potential loss of very distinctive neighbourhoods and to introduce particular characteristics of urban spaces and the way migrant communities appropriate them. The socio-spatial practice of these communities is explored to identify their impact on contemporary urban spaces as well as the future challenges of providing efficient urban environments for social groups with limited purchasing power. Methodologically, as part of a learning experiment undertaken at Qatar University, structured field surveys, environmental systematic observations as well as behavioural mapping are adopted as important approaches to investigation. While the investigation reveals interesting dynamics between migrant communities and their environments, it also postulate that city residents have capacity to recover quickly from difficulties; toughness in spite of a domineering and hampering context. The paper concludes with projections of how contemporary transformation processes in Gulf cities will have to be based on social inclusion and the recognition that migrant communities need to have access to develop their own settings that relate to their needs and routine spatial practices while securing the economic basis of many migrants and providing better living standards for all communities. The initiation of holistic and integrated development strategies is of high significance for both the preservation of historic districts in order to secure the roots of Doha as well as for migrant communities, who are facing the potential loss of their businesses and familiar surroundings

Magnetoresistance oscillations in multilayer systems - triple quantum wells

Magnetoresistance of two-dimensional electron systems with several occupied subbands oscillates owing to periodic modulation of the probability of intersubband transitions by the quantizing magnetic field. In addition to previous investigations of these magneto-intersubband (MIS) oscillations in two-subband systems, we report on both experimental and theoretical studies of such a phenomenon in three-subband systems realized in triple quantum wells. We show that the presence of more than two subbands leads to a qualitatively different MIS oscillation picture, described as a superposition of several oscillating contributions. Under a continuous microwave irradiation, the magnetoresistance of triple-well systems exhibits an interference of MIS oscillations and microwaveinduced resistance oscillations. The theory explaining these phenomena is presented in the general form, valid for an arbitrary number of subbands. A comparison of theory and experiment allows us to extract temperature dependence of quantum lifetime of electrons and to confirm the applicability of the inelastic mechanism of microwave photoresistance for the description of magnetotransport in multilayer systems.Comment: 10 pages, 5 figure

The everyday urban environment of migrant labourers in Gulf Cities: the case of the old centre of Doha, Qatar

© 2017, The Author(s). Preventing the complete social restructuring and the relocation of migrant communities from traditional cores in Gulf cities to newly urbanized areas is a rising urban and social challenge. The Al Asmakh district in the old centre of Doha is an important example that manifests the current encounter between rising investment pressures and preserving the local identity including the particular urban life and spatial settings that have evolved over several decades. This paper presents key research findings with respect to the lived urban spaces of the Al Asmakh in order to exemplify the potential loss of very distinctive neighbourhoods and to introduce particular characteristics of urban spaces and the way migrant communities appropriate them. As part of a learning experiment undertaken at Qatar University in 2014, structured field surveys, systematic observations as well as behavioural mapping techniques were adopted as important approaches to investigation. The outcomes reveal stimulating dynamics between migrant communities and their environments. It also postulates that city residents have the capacity to recover swiftly from difficulties and resilience in spite of an impeding and hampering context. The paper concludes with projections of how contemporary transformation processes in Gulf cities will have to be based on diversity and social inclusion. Such a transformation should stem from the recognition that migrant communities need to have access to develop their own settings that relate to their routine spatial practices while securing the economic basis of many migrant labourers