A flowing plasma model to describe drift waves in a cylindrical helicon discharge

A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetised plasma (WOMBAT), with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalised rotation frequency, lower temperature and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature non-uniformity and magnetic field oscillations, are also discussed

New two in one magnetic fluorescent nanocomposites

Magnetite nanoparticles have been coated by a porphyrin derivative to produce new magnetic materials with fluorescent properties. The magnetic nanoparticles were prepared using two different methods, one based on sol-gel techniques and ultrasonic processing, and the other via a controlled chemical co-precipitation. Different types of porphyrin functionalised magnetic nanoparticles have been prepared and have been characterised by electron microscopy (TEM and SEM), XRD, FTIR, Raman, UV-vis, and fluorescence spectroscopy. Microscopy results showed the formation of core-shell nanostructures, with IR and photoluminescence spectroscopy results confirming the presence of porphyrin in the shell

A facial expression for anxiety.

Anxiety and fear are often confounded in discussions of human emotions. However, studies of rodent defensive reactions under naturalistic conditions suggest anxiety is functionally distinct from fear. Unambiguous threats, such as predators, elicit flight from rodents (if an escape-route is available), whereas ambiguous threats (e.g., the odor of a predator) elicit risk assessment behavior, which is associated with anxiety as it is preferentially modulated by anti-anxiety drugs. However, without human evidence, it would be premature to assume that rodent-based psychological models are valid for humans. We tested the human validity of the risk assessment explanation for anxiety by presenting 8 volunteers with emotive scenarios and asking them to pose facial expressions. Photographs and videos of these expressions were shown to 40 participants who matched them to the scenarios and labeled each expression. Scenarios describing ambiguous threats were preferentially matched to the facial expression posed in response to the same scenario type. This expression consisted of two plausible environmental-scanning behaviors (eye darts and head swivels) and was labeled as anxiety, not fear. The facial expression elicited by unambiguous threat scenarios was labeled as fear. The emotion labels generated were then presented to another 18 participants who matched them back to photographs of the facial expressions. This back-matching of labels to faces also linked anxiety to the environmental-scanning face rather than fear face. Results therefore suggest that anxiety produces a distinct facial expression and that it has adaptive value in situations that are ambiguously threatening, supporting a functional, risk-assessing explanation for human anxiet

The internal layering of Pine Island Glacier, West Antarctica, from airborne radar-sounding data

This paper presents an overview of internal layering across Pine Island Glacier, West Antarctica, as measured from airborne-radar data acquired during a survey conducted by the British Antarctic Survey and the University of Texas in the 2004/05 season. Internal layering is classified according to type (continuous/discontinuous/missing) and the results compared with InSAR velocities. Several areas exhibit disruption of internal layers that is most likely caused by large basal shear stresses. Signs of changes in flow were identified in a few inter-tributary areas, but overall the layering classification and distribution of layers indicate that only minor changes in ice-flow regime have taken place. This is supported by bed-topography data that show the main trunk of the glacier, as well as some of the tributaries, are topographically controlled and located in deep basins

Exploiting cation aggregation in new magnesium amidohaloaluminate electrolytes for magnesium batteries

Mg batteries present an attractive and sustainable alternative to Li-ion batteries, wherein magnesium metal as an anode displays a superior theoretical volumetric energy density of 3833 A h L−1versus 2062 A h L−1 for lithium. An outstanding crucial bottleneck in realising their more widespread uptake is the development of suitable electrolytes, where electrode passivation, a limited electrochemical window, conditioning requirements, low ion mobility and low coulombic efficiencies all contribute to current limitations in Mg batteries. In an area thus far dominated by the thermodynamically stable [Mg2Cl3]+ dinuclear cation, we present here a novel family of magnesium amidohaloaluminate electrolytes [(Dipp)(SiMe3)2NAlCl3]− [MgxCl2x−1]+ where the magnesium chloride cation aggregation has been tailored (x = 1, 2, 3) by substitution of the coordinating ligand to the Mg2+ centre, and show how directly altering this cation affects battery performance (Dipp = 2,6-diisopropylphenyl, Me = methyl). The electrochemical activity of these new electrolytes has been evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy in Mg–metal symmetrical cells as well as in battery cells with the Mo6S8 Chevrel phase cathode material against magnesium metal. The mononuclear and dinuclear magnesium amidohaloaluminate electrolytes facilitate reversible Mg plating and stripping from the Mg–metal anode with excellent stability, withstanding over 70 hours of continuous cycling. We demonstrate the compatibility of these novel electrolytes with the Mo6S8 Chevrel intercalation cathode material, allowing cycling of a Mg–metal cell up to 100 cycles with coulombic efficiencies above 95%

Worthwhile work? Childcare, feminist ethics and cooperative research practices

Interdisciplinary research collaborations are often encouraged within higher education while the practicalities of such collaborations are glossed over. This project specifically addresses the praxis of research collaborations, exploring how feminist academics within different countries and disciplines came together to explore their mutual concern about the perceived worth and well-being of early childhood practitioners. Engaging in a formal methodological dialogue over eight months, seven academics discussed, analysed and dissected their different investments in research methods and intents, with the aim of agreeing to a common methodological framework. Unexpectedly, what emerged was not a product, but a process. We argue that this process offers much to those seeking deep collaboration in and through shared research. Building on a collective research interest, we found ourselves in a process of becoming, germinating the seed of a transnational research cooperative, based on trust and mutual respect, rather than the arid methodological contract originally envisioned

Microwave-assisted synthesis and electrochemical evaluation of VO2 (B) nanostructures

Understanding how intercalation materials change during electrochemical operation is paramount to optimizing their behaviour and function and in situ characterization methods allow us to observe these changes without sample destruction. Here we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave-assisted route which exhibits a larger electrochemical capacity (232 mAh g-1) compared with VO2 (B) prepared by a solvothermal route (197 mAh g-1). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during battery operation

Group and individual analyses of pre-, peri-, and post-movement related alpha and beta oscillations during a single continuous monitoring task

Band power linked to lower and upper alpha (i.e. 8-10Hz; 10-12Hz) and lower and upper beta (i.e. 12-20Hz; 20-30Hz) were examined during response related stages, including anticipation, response execution (RE), response inhibition (RI) and post response recovery (PRR). Group and individual data from 34 participants were considered. The participant’s objective was to press a response key immediately following 4 non-repeating, single integer odd digits. These were presented amongst a continuous stream of digits and Xs. Electroencephalogram (EEG) signals were recorded from 32 electrodes (pooled to 12 regions). In the group analyses, participant EEG response was compared to baseline revealing that upper alpha desynchronised during anticipation, RE and RI; lower beta during anticipation and RE; and upper beta just RE. Upper alpha desynchronisation during rapid, unplanned RI is novel. Also, upper alpha and lower/upper beta synchronised during PRR. For upper alpha, we speculate this indexes brief cortical deactivation; for beta we propose this indexes response set maintenance. Lastly, lower alpha fluctuations correlated negatively with RT, indexing neural efficiency. Individual analyses involved calculation of the proportion of individuals displaying the typical RE and PRR trends; these were not reflected by all participants. The former was displayed individually by the largest proportion in upper alpha recorded left fronto-centrally; the latter was most reliably displayed individually in lower beta recorded mid centro-parietally. Therefore, group analyses identified typical alpha and beta synchronisation/ desynchronisation trends, whilst individual analyses identified their degree of representation in single participants. Attention is drawn to the clinical relevance of this issue