1,146 research outputs found
On the Margins of Ghana and Kawkaw: Four seasons of excavation at Tongo Maaré Diabal (AD 500-1150), Mali
This article summarises the results of four seasons of excavation at Tongo Maaré Diabal (AD 500-1150), near Douentza, Mali. Deep stratigraphic excavations were directed by MacDonald and Togola in 1993, 1995 and by MacDonald in 1996. Complementary, large exposure excavations of the abandonment layer were undertaken by Gestrich in 2010. The combined excavation results speak to topics of craft specialisation, trade, and social organisation. They provide evidence of a specialised blacksmithing community situated at the margins of early Middle Niger and Niger Bend statehood and urbanisation.Le présent article porte sur les résultats de quatre saisons de fouilles sur le site de Tongo Maaré Diabal (AD 500-1150), non loin de la ville de Douentza au Mali. Des fouilles stratigraphiques en profondeur ont été réalisées par MacDonald et Togola en 1993 et 1995 ; et par MacDonald en 1996. Des fouilles complémentaires du dernier horizon d’occupation ont été réalisées sur une grande surface par Gestrich en 2010. Les résultats de ces campagnes portent sur des thèmes de la spécialisation artisanale, du commerce et de l’organisation sociale. Ils nous permettent de décrire une communauté des métallurgistes spécialisées, située en marges des anciens développements étatiques et urbains du Moyen Niger et de la Boucle du Niger.This article is in English
Windé Koroji Ouest (Mali, Second and Third Millennia BCE): The Environmental and Subsistence Evidence
Windé Koroji Ouest is an early agro-pastoral site situated at the eastern periphery of the Inland Niger Delta of Mali,
north of the Gandamia and Bandiagara escarpments. This chapter is the first publication of all subsistence and environmental information available concerning this site which was excavated by the senior author in 1992/1993. The
presence of domestic millet ca. 2100-1900 BCE is confirmed, as well as sheep during this same period, with cattle
attested subsequently (post 1600 BCE). The role of the environment and potential environmental change in the economy of this site is reviewed. It is argued that Windé Koroji Ouest existed within wider, seasonally mobile settlement
networks exhibiting a range of flexible subsistence adaptations
Atom-by-Atom Substitution of Mn in GaAs and Visualization of their Hole-Mediated Interactions
The discovery of ferromagnetism in Mn doped GaAs [1] has ignited interest in
the development of semiconductor technologies based on electron spin and has
led to several proof-of-concept spintronic devices [2-4]. A major hurdle for
realistic applications of (Ga,Mn)As, or other dilute magnetic semiconductors,
remains their below room-temperature ferromagnetic transition temperature.
Enhancing ferromagnetism in semiconductors requires understanding the
mechanisms for interaction between magnetic dopants, such as Mn, and
identifying the circumstances in which ferromagnetic interactions are maximized
[5]. Here we report the use of a novel atom-by-atom substitution technique with
the scanning tunnelling microscope (STM) to perform the first controlled atomic
scale study of the interactions between isolated Mn acceptors mediated by the
electronic states of GaAs. High-resolution STM measurements are used to
visualize the GaAs electronic states that participate in the Mn-Mn interaction
and to quantify the interaction strengths as a function of relative position
and orientation. Our experimental findings, which can be explained using
tight-binding model calculations, reveal a strong dependence of ferromagnetic
interaction on crystallographic orientation. This anisotropic interaction can
potentially be exploited by growing oriented Ga1-xMnxAs structures to enhance
the ferromagnetic transition temperature beyond that achieved in randomly doped
samples. Our experimental methods also provide a realistic approach to create
precise arrangements of single spins as coupled quantum bits for memory or
information processing purposes
Controlling Curie temperature in (Ga,Ms)As through location of the Fermi level within the impurity band
The ferromagnetic semiconductor (Ga,Mn)As has emerged as the most studied
material for prototype applications in semiconductor spintronics. Because
ferromagnetism in (Ga,Mn)As is hole-mediated, the nature of the hole states has
direct and crucial bearing on its Curie temperature TC. It is vigorously
debated, however, whether holes in (Ga,Mn)As reside in the valence band or in
an impurity band. In this paper we combine results of channeling experiments,
which measure the concentrations both of Mn ions and of holes relevant to the
ferromagnetic order, with magnetization, transport, and magneto-optical data to
address this issue. Taken together, these measurements provide strong evidence
that it is the location of the Fermi level within the impurity band that
determines TC through determining the degree of hole localization. This finding
differs drastically from the often accepted view that TC is controlled by
valence band holes, thus opening new avenues for achieving higher values of TC.Comment: 5 figures, supplementary material include
A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore
The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear ‘marking trees’ to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively ‘safe’ time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears
Visualisation to enhance biomechanical tuning of ankle-foot orthoses (AFOs) in stroke: study protocol for a randomised controlled trial
There are a number of gaps in the evidence base for the use of ankle-foot orthoses for stroke patients. Three dimensional motion analysis offers an ideal method for objectively obtaining biomechanical gait data from stroke patients, however there are a number of major barriers to its use in routine clinical practice. One significant problem is the way in which the biomechanical data generated by these systems is presented. Through the careful design of bespoke biomechanical visualisation software it may be possible to present such data in novel ways to improve clinical decision making, track progress and increase patient understanding in the context of ankle-foot orthosis tuning
Widespread active detachment faulting and core complex formation near 13°N on the Mid-Atlantic Ridge
Author Posting. © Nature Publishing Group, 2006. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 442 (2006): 440-443, doi:10.1038/nature04950.Oceanic core complexes are massifs in which lower crustal and upper mantle rocks are exposed at the sea floor. They form at mid-ocean ridges through slip on detachment faults rooted below the spreading axis. To date, most studies of core complexes have been based on isolated inactive massifs that have spread away from ridge axes. A new survey of the Mid-Atlantic Ridge (MAR) near 13°N reveals a segment in which a number of linked detachment faults extend for 75 km along one flank of the spreading axis. The detachment faults are apparently all currently active and at various stages of development. A field of extinct core complexes extends away from the axis for at least 100 km. The new data document the topographic characteristics of actively-forming core complexes and their evolution from initiation within the axial valley floor to maturity and eventual inactivity. Within the surrounding region there is a strong correlation between detachment fault morphology at the ridge axis and high rates of hydroacoustically-recorded earthquake seismicity. Preliminary examination of seismicity and seafloor morphology farther north along the MAR suggests that active detachment faulting is occurring in many segments and that detachment faulting is more important in the generation of ocean crust at this slow-spreading ridge than previously suspected.This work was supported by the National Science Foundation
Social media use, attitudes, behaviours and perceptions of online professionalism amongst dental students
Use of social media has increased amongst health professionals. This has benefits for patient care but also introduces risks for confidentiality and professional fitness to practise. This study aimed to examine dental student attitudes towards professional behaviour on social media. The secondary aim was to establish the extent and nature of social media use and exposure to potentially unprofessional behaviours.
A cross-sectional study was carried out in one dental school. Data were collected using questionnaires to examine social media use, perceptions and attitudes towards social media and professional behaviours online. Students who responded (n=155) all used social media at least once per week; most used more than one platform. Students were aware of the relationship between social media use and professional practice. Posting drunken photographs and interacting with staff and patients online were widely considered as unprofessional. Security settings affected behaviour and most had seen inappropriate behaviours online.
Students use social media extensively. Students are aware of the risks but there is a greater sense of safety in closed groups and many students are exposed to potentially inappropriate content online. This suggests that there are opportunities to reduce these risks through training to help students manage these risks
- …