Direct Detection of Galactic Halo Dark Matter

The Milky Way Galaxy contains a large, spherical component which is believed to harbor a substantial amount of unseen matter. Recent observations indirectly suggest that as much as half of this ``dark matter'' may be in the form of old, very cool white dwarfs, the remnants of an ancient population of stars as old as the Galaxy itself. We conducted a survey to find faint, cool white dwarfs with large space velocities, indicative of their membership in the Galaxy's spherical halo component. The survey reveals a substantial, directly observed population of old white dwarfs, too faint to be seen in previous surveys. This newly discovered population accounts for at least 2% of the halo dark matter. It provides a natural explanation for the indirect observations, and represents a direct detection of Galactic halo dark matter.Comment: 13 pages, 4 figures, 1 table. Note added after Science Express online publication: This text reflects the correction of a few typographical errors in the online version of the table. It also includes the new constraint on the calculation of d_max which accounts for the fact that the survey could not have detected stars with proper motions below 0.33 arcseconds per year. Published online at ScienceExpress www.sciencemag.org 22 March 2001; 10.1126/science.1059954; To appear in Science 27 April 200

Young children’s creativity in science enquiry: a diffractive analysis of empirical and theoretical understandings

Little attention has been paid to the materiality of children’s creative knowledge making practices in science enquiry. Conflicting discourses have instead shaped a narrow understanding of how children come to know in early childhood science education. This thesis draws on new materialist philosophy to offer a new approach to diffractive analysis by showing how critical points of difference are created when empirical data encounter theoretical perspectives diffractively. In doing so, conflicting discourses are challenged as limiting, and points of difference illuminated as crucial in affecting connections which can convincingly reconfigure dominant ways of seeing. The thesis firstly presents empirical data which illustrates shared understandings of creativity in science enquiry held by early childhood practitioners, gathered using Video Stimulated Reflective Dialogues (Moyles et al., 2003) and analysed using a grounded theoretical approach. This data was found to be largely representative of existing perspectives on young children’s creativity in science enquiry and the analysis restricted by theoretical, ontological and axiological norms within the interpretivist paradigm. The empirical data was subsequently ‘re-turned’ in a diffraction together with i) existing research on early childhood science education, and ii) conceptualisations of creativity in the domain of art, to reveal critical points of difference which, in superposition, create the possibility for a new conceptualisation of young children’s creativity in science enquiry. Consideration is given to the role and ethics of what is excluded in reading diffractively. A diffractive reading found children’s creativity in science enquiry to be enacted at once through talk and materials. Cutting together and apart child-material revealed children as decentred and coming to know through the materiality of materials. This opens possibilities to explore children’s co-constitutive and affective ways of knowing in science enquiry. Attention is drawn to both video camera and footage as more-than-human matter and the need for further research into the significance of points of difference potentially emergent from the spaces in-between children’s encounters with materials in science enquiry

Diffractive encounters with empirical and theoretical understandings of children’s creativity in science enquiry

Diffractive methodology is a recently established alternative to the interpretivist approach commonly used in educational research. Unlike epistemological practices grounded in representation, it recognises knowledge making as performative and emergent from difference. This paper offers new insights into diffractive readings in early childhood science education through experimentation with entangled empirical video data, theoretical perspectives and transdisciplinary space. A methodological contribution is made by showing how critical points of difference are created when video footage of shared understandings held by early childhood practitioners encounters existing research on early childhood science education diffractively. These points of difference are made to matter and illuminated as affecting emergent new connections which can reconfigure dominant ways of understanding creativity in early childhood science education. In doing so, children’s creative knowledge making practices in science enquiry are (re)presented as expansive, material knowing which is enacted at once through talk and materials

Communicating REDD+ Issues at Local Level: Creating Latent and Manifest Conflict

”Carbon offsetting”in forestry-related projects is widely regarded as the ideal solution to the three challenges of the 21st Century: climate change, biodiversity conservation andsocio-economic development. At the same time, there is scepticism about the Reducing Emissions from Deforestation and Forest Degradation (REDD) proposal particularly because of the weak governance and institutional capacities in many developing countries, which could jeopardize the delivery of benefits at the local level. One major problem is that most people have little knowledge on the causes and consequences of the climate change. This is partly because the information is largely scattered among scientific journals, and obscured by jargon and sophisticated mathematical models. Consequently, REDD+ is beyond thereach of manyof the people affected by REDD+. This paper examines the efforts and the capacity of the local governments and other development agents in explaining the REDD + issues and its impacts on the local people, especially customary communities. The research shows that lack of policy communication and promotion, as well as consultations with the affected groups arethe main contributing factors to latent and manifest conflicts. In turn, this conflicth as proven that NGOs, district governments and scientists have not been successful intermediaries. Thus, in the future policy communication on REDD+ should beaimed at improved network formation (i.e. between farmer groups with business partners and NGOs and other related actors), learning, negotiation and relationship building (i.e. between members of farmer groups, not only withtheir leaders within the farmer groups but also with governmental and business sectors). Policy communication should also create a new configuration of support and services in form of advocacy, empowerment and management skills and technical skills for conserving their natural resources, for adaptation to climate change and building more equitable governance and transparency at local level

Lactation transcriptomics in the Australian marsupial, Macropus eugenii: transcript sequencing and quantification

<p>Abstract</p> <p>Background</p> <p>Lactation is an important aspect of mammalian biology and, amongst mammals, marsupials show one of the most complex lactation cycles. Marsupials, such as the tammar wallaby (<it>Macropus eugenii</it>) give birth to a relatively immature newborn and progressive changes in milk composition and milk production regulate early stage development of the young.</p> <p>Results</p> <p>In order to investigate gene expression in the marsupial mammary gland during lactation, a comprehensive set of cDNA libraries was derived from lactating tissues throughout the lactation cycle of the tammar wallaby. A total of 14,837 express sequence tags were produced by cDNA sequencing. Sequence analysis and sequence assembly were used to construct a comprehensive catalogue of mammary transcripts.</p> <p>Sequence data from pregnant and early or late lactating specific cDNA libraries and, data from early or late lactation massively parallel sequencing strategies were combined to analyse the variation of milk protein gene expression during the lactation cycle.</p> <p>Conclusion</p> <p>Results show a steady increase in expression of genes coding for secreted protein during the lactation cycle that is associated with high proportion of transcripts coding for milk proteins. In addition, genes involved in immune function, translation and energy or anabolic metabolism are expressed across the lactation cycle. A number of potential new milk proteins or mammary gland remodelling markers, including noncoding RNAs have been identified.</p

SSSPM J1444-2019: an extremely high proper motion, ultracool subdwarf

We present the discovery of a new extreme high proper motion object (3.5 arcsec/year) which we classify as an ultracool subdwarf with [M/H] = -0.5. It has a formal spectral type of sdM9 but also shows L-type features: while the VO bands are completely absent, it exhibits extremely strong TiO absorption in its optical spectrum. With a radial velocity of about -160 km/s and a rough distance estimate of 16--24 pc, it is likely one of the nearest halo members crossing the Solar neighbourhood with a heliocentric space velocity of (U,V,W)=(-244,-256,-100)+/-(32,77,6) km/s.Comment: 4 pages, 4 figures (Fig.1a-d available as jpg files), accepted for publication in Astronomy & Astrophysics Letter

Cholinergic modulation of Up–Down states in the mouse medial entorhinal cortex in vitro

Cholinergic tone is high during wake and rapid eye movement sleep and lower during slow wave sleep (SWS). Nevertheless, the low tone of acetylcholine during SWS modulates sharp wave ripple incidence in the hippocampus and slow wave activity in the neocortex. Linking the hippocampus and neocortex, the medial entorhinal cortex (mEC) regulates the coupling between these structures during SWS, alternating between silent Down states and active Up states, which outlast neocortical ones. Here, we investigated how low physiological concentrations of acetylcholine (ACh; 100‐500 nM) modulate Up and Down states in a mEC slice preparation. We find that ACh has a dual effect on mEC activity: it prolongs apparent Up state duration as recorded in individual cells and decreases the total synaptic charge transfer, without affecting the duration of detectable synaptic activity. The overall outcome of ACh application is excitatory and we show that ACh increases Up state incidence via muscarinic receptor activation. The mean firing rate of principal neurons increased in around half of the cells while the other half showed a decrease in firing rate. Using two‐photon calcium imaging of population activity, we found that population‐wide network events are more frequent and rhythmic during ACh and confirmed that ACh modulates cell participation in these network events, consistent with a role for cholinergic modulation in regulating information flow between the hippocampus and neocortex during SWS

Granular Packings: Nonlinear elasticity, sound propagation and collective relaxation dynamics

Experiments on isotropic compression of a granular assembly of spheres show that the shear and bulk moduli vary with the confining pressure faster than the 1/3 power law predicted by Hertz-Mindlin effective medium theories (EMT) of contact elasticity. Moreover, the ratio between the moduli is found to be larger than the prediction of the elastic theory by a constant value. The understanding of these discrepancies has been a longstanding question in the field of granular matter. Here we perform a test of the applicability of elasticity theory to granular materials. We perform sound propagation experiments, numerical simulations and theoretical studies to understand the elastic response of a deforming granular assembly of soft spheres under isotropic loading. Our results for the behavior of the elastic moduli of the system agree very well with experiments. We show that the elasticity partially describes the experimental and numerical results for a system under compressional loads. However, it drastically fails for systems under shear perturbations, particularly for packings without tangential forces and friction. Our work indicates that a correct treatment should include not only the purely elastic response but also collective relaxation mechanisms related to structural disorder and nonaffine motion of grains.Comment: 21 pages, 13 figure