Cumulenic and heterocumulenic anions : potential interstellar species?

A recent theoretical investigation by Terzieva & Herbst of linear carbon chains, C-n where n greater than or equal to 6, in the interstellar medium has shown that these species can undergo efficient radiative association to form the corresponding anions. An experimental study by Barckholtz, Snow & Bierbaum of these anions has demonstrated that they do not react efficiently with molecular hydrogen, leading to the possibility of detectable abundances of cumulene-type anions in dense interstellar and circumstellar environments. Here we present a series of electronic structure calculations which examine possible anionic candidates for detection in these media, namely the anion analogues of the previously identified interstellar cumulenes CnH and Cn-1CH2 and heterocumulenes CnO (where n = 2-10). The extraordinary electron affinities calculated for these molecules suggest that efficient radiative electron attachment could occur, and the large dipole moments of these simple (generally) linear molecules point to the possibility of detection by radio astronomy.

Trait and behavioural motor control is associated with resistance to overconsumption

While overall obesity rates are rising, a minority of individuals appear to resist overconsumption and remain lean in spite of an ‘obesogenic’ environment. Studying the factors hypothesised to underpin behaviours associated with resistance to overconsumption may inform weight management strategies in an adverse environment. Trait (BIS-11) and behavioural (response inhibition, GoStop) self control were assessed in the laboratory. Snack food consumption was measured covertly via a sham taste test. Lack of motor control was positively correlated (r = .32, p <. 05) and successful response inhibition was negatively correlated (r = −.35, p <. 05) with snack food intake. Low motor control was also associated with further food intake when satiated (r = .39, p < .01). These relationships were independent of self-reported palatability and perceived reward value of the food. Motor control may be an important factor implicated in ‘mindless’ eating in an environment abundant in palatable, energy-dense snack foods.

Dormant but migratory tumour cells in desmoplastic stroma of invasive ductal carcinomas

Mortality in breast cancer is linked to metastasis and recurrence yet there is no acceptable biological model for cancer relapse. We hypothesise that there might exist primary tumour cells capable of escaping surgery by migration and resisting radiotherapy and chemotherapy to cause cancer recurrence. We investigated this possibility in invasive ductal carcinoma (IDC) tissue and observed the presence of solitary primary tumour cells (SPCs) in the dense collagen stroma that encapsulates intratumoural cells (ICs). In IDC tissue sections, collagen was detected with either Masson's Trichrome or by second harmonics imaging. Cytokeratin-19 (CK-19) and vimentin (VIM) antibodies were, respectively, used to identify epithelial-derived tumour cells and to indicate epithelial to mesenchymal transition (EMT). Confocal/multiphoton microscopy showed that ICs from acini were mainly CK-19 +ve and were encapsulated by dense stromal collagen. Within the stroma, SPCs were detected by their staining for both CK-19 and VIM (confirming EMT). ICs and SPCs were subsequently isolated by laser capture microdissection followed by multiplex tandem-PCR studies. SPCs were found to be enriched for pro-migratory and anti-proliferative genes relative to ICs. In vitro experiments using collagen matrices at 20 mg/cm 3, similar in density to tumour matrices, demonstrated that SPC-like cells were highly migratory but dormant, phenotypes that recapitulated the genotypes of SPCs in clinical tissue. These data suggest that SPCs located at the breast cancer perimeter are invasive and dormant such that they may exceed surgical margins and resist local and adjuvant therapies. This study has important connotations for a role of SPCs in local recurrence.

A light and electron microscopic study of NADPH-diaphorase-,calretinin- and parvalbumin-containing neurons in the rat nucleus accumbens

The rat nucleus accumbens contains medium-sized, spiny projection neurons and intrinsic, local circuit neurons, or interneurons. Sub-classes of interneurons, revealed by calretinin (CR) or parvalbumin (PV) immunoreactivity or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, were compared in the nucleus accumbens core, shell and rostral pole. CR, PV and NADPH-diaphorase-containing neurons are shown to form three non-co-localising populations in these three areas. No significant differences in neuronal population densities were found between the subterritories. NADPH-diaphorase-containing neurons could be further separated morphologically into three sub-groups, but CR- and PV-immunoreactive neurons form homogeneous populations. Ultrastructurally, NADPH-diaphorase-, CR- and PV-containing neurons in the nucleus accumbens all possess nuclear indentations. These are deeper and fewer in neurons immunoreactive for PV than in CR- and NADPH-diaphorase-containing neurons. CR-immunoreactive boutons form asymmetrical and symmetrical synaptic specialisations on spines, dendrites and somata, while PV-immunoreactive boutons make only symmetrical synaptic specialisations. Both CR- and PV-immunoreactive boutons form symmetrical synaptic specialisations with medium-sized spiny neurons and contact other CR- and PV-immunoreactive somata, respectively. A novel non-carcinogenic substrate for the peroxidase reaction (Vector Slate Grey, SG) was found to be characteristically electron-dense and may be distinguishable from the diaminobenzidine reaction product. We conclude that the three markers used in this study are localised in distinct populations of nucleus accumbens interneurons. Our studies of their synaptic connections contribute to an increased understanding of the intrinsic circuitry of this area.

Identifying the spatial scale of land use that most strongly influences overall river ecosystem health score

Catchment and riparian degradation has resulted in declining ecosystem health of streams worldwide. With restoration a priority in many regions, there is an increasing interest in the scale at which land use influences stream ecosystem health. Our goal was to use a substantial data set collected as part of a monitoring program (the Southeast Queensland, Australia, Ecological Health Monitoring Program data set, collected at 116 sites over six years) to identify the spatial scale of land use, or the combination of spatial scales, that most strongly influences overall ecosystem health. In addition, we aimed to determine whether the most influential scale differed for different aspects of ecosystem health. We used linear-mixed models and a Bayesian model-averaging approach to generate models for the overall aggregated ecosystem health score and for each of the five component indicators (fish, macroinvertebrates, water quality, nutrients, and ecosystem processes) that make up the score. Dense forest close to the survey site, mid-dense forest in the hydrologically active nearstream areas of the catchment, urbanization in the riparian buffer, and tree cover at the reach scale were all significant in explaining ecosystem health, suggesting an overriding influence of forest cover, particularly close to the stream. Season and antecedent rainfall were also important explanatory variables, with some land-use variables showing significant seasonal interactions. There were also differential influences of land use for each of the component indicators. Our approach is useful given that restoring general ecosystem health is the focus of many stream restoration projects; it allowed us to predict the scale and catchment position of restoration that would result in the greatest improvement of ecosystem health in the regions streams and rivers. The models we generated suggested that good ecosystem health can be maintained in catchments where 80% of hydrologically active areas in close proximity to the stream have mid-dense forest cover and moderate health can be obtained with 60% cover.

A sparse hybrid map for vision-guided mobile robots

This paper introduces a minimalistic approach to produce a visual hybrid map of a mobile robot’s working environment. The proposed system uses omnidirectional images along with odometry information to build an initial dense posegraph map. Then a two level hybrid map is extracted from the dense graph. The hybrid map consists of global and local levels. The global level contains a sparse topological map extracted from the initial graph using a dual clustering approach. The local level contains a spherical view stored at each node of the global level. The spherical views provide both an appearance signature for the nodes, which the robot uses to localize itself in the environment, and heading information when the robot uses the map for visual navigation. In order to show the usefulness of the map, an experiment was conducted where the map was used for multiple visual navigation tasks inside an office workplace.

Low-temperature plasma processing for Si photovoltaics

There has been a recent rapid expansion of the range of applications of low-temperature plasma processing in Si-based photovoltaic (PV) technologies. The desire to produce Si-based PV materials at an acceptable cost with consistent performance and reproducibility has stimulated a large number of major research and research infrastructure programs, and a rapidly increasing number of publications in the field of low-temperature plasma processing for Si photovoltaics. In this article, we introduce the low-temperature plasma sources for Si photovoltaic applications and discuss the effects of low-temperature plasma dissociation and deposition on the synthesis of Si-based thin films. We also examine the relevant growth mechanisms and plasma diagnostics, Si thin-film solar cells, Si heterojunction solar cells and silicon nitride materials for antireflection and surface passivation. Special attention is paid to the low-temperature plasma interactions with Si materials including hydrogen interaction, wafer cleaning, masked or mask-free surface texturization, the direct formation of p-n junction, and removal of phosphorus silicate glass or parasitic emitters. The chemical and physical interactions in such plasmas with Si surfaces are analyzed. Several examples of the plasma processes and techniques are selected to represent a variety of applications aimed at the improvement of Si-based solar cell performance. © 2014 Elsevier B.V.

Defects induced ferromagnetism in plasma-enabled graphene nanopetals

Ferromagnetism in graphene is fascinating, but it is still a big challenge for practical applications due to the weak magnetization. In order to enhance the magnetization, here, we design plasma-enabled graphene nanopetals with ultra-long defective edges of up to 105 m/g, ultra-dense lattice vacancies, and hydrogen chemisorptions. The designed graphene nanopetals display robust ferromagnetism with large saturation magnetization of up to 2 emu/g at 5 K and 1.2 emu/g at room temperatures. This work identifies the plasma-enabled graphene nanopetals as a promising candidate for graphene-based magnetic devices.

Plasma-produced phase-pure cuprous oxide nanowires for methane gas sensing

Phase-selective synthesis of copper oxide nanowires is warranted by several applications, yet it remains challenging because of the narrow windows of the suitable temperature and precursor gas composition in thermal processes. Here, we report on the room-temperature synthesis of small-diameter, large-area, uniform, and phase-pure Cu2O nanowires by exposing copper films to a custom-designed low-pressure, thermally non-equilibrium, high-density (typically, the electron number density is in the range of 10 11-1013cm-3) inductively coupled plasmas. The mechanism of the plasma-enabled phase selectivity is proposed. The gas sensors based on the synthesized Cu2O nanowires feature fast response and recovery for the low-temperature (∼140°C) detection of methane gas in comparison with polycrystalline Cu2O thin film-based gas sensors. Specifically, at a methane concentration of 4%, the response and the recovery times of the Cu2O nanowire-based gas sensors are 125 and 147s, respectively. The Cu2O nanowire-based gas sensors have a potential for applications in the environmental monitoring, chemical industry, mining industry, and several other emerging areas.

Atmospheric gas plasma–induced ROS production activates TNF-ASK1 pathway for the induction of melanoma cancer cell apoptosis

Atmospheric gas plasmas (AGPs) are able to selectively induce apoptosis in cancer cells, offering a promising alternative to conventional therapies that have unwanted side effects such as drug resistance and toxicity. However, the mechanism of AGP-induced cancer cell death is unknown. In this study, AGP is shown to up-regulate intracellular reactive oxygen species (ROS) levels and induce apoptosis in melanoma but not normal melanocyte cells. By screening genes involved in apoptosis, we identify tumor necrosis factor (TNF)-family members as the most differentially expressed cellular genes upon AGP treatment of melanoma cells. TNF receptor 1 (TNFR1) antagonist-neutralizing antibody specifically inhibits AGP-induced apoptosis signal, regulating apoptosis signal-regulating kinase 1 (ASK1) activity and subsequent ASK1-dependent apoptosis. Treatment of cells with intracellular ROS scavenger N-acetyl-l-cysteine also inhibits AGP-induced activation of ASK1, as well as apoptosis. Moreover, depletion of intracellular ASK1 reduces the level of AGP-induced oxidative stress and apoptosis. The evidence for TNF-signaling dependence of ASK1-mediated apoptosis suggests possible mechanisms for AGP activation and regulation of apoptosis-signaling pathways in tumor cells.

Guided ionization waves : theory and experiments

This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves-streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures-sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures-plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g.,He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path-the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology.

Large networks of vertical multi-layer graphenes with morphology-tunable magnetoresistance

We report on the comparative study of magnetotransport properties of large-area vertical few-layer graphene networks with different morphologies, measured in a strong (up to 10 T) magnetic field over a wide temperature range. The petal-like and tree-like graphene networks grown by a plasma enhanced CVD process on a thin (500 nm) silicon oxide layer supported by a silicon wafer demonstrate a significant difference in the resistance-magnetic field dependencies at temperatures ranging from 2 to 200 K. This behaviour is explained in terms of the effect of electron scattering at ultra-long reactive edges and ultra-dense boundaries of the graphene nanowalls. Our results pave a way towards three-dimensional vertical graphene-based magnetoelectronic nanodevices with morphology-tuneable anisotropic magnetic properties. © The Royal Society of Chemistry 2013.

Plasma foundations and nanoscience : the plasma-plasmonics junction

Plasma science and plasmonics are connected by very similar physics, in particular, the notion of collective plasma waves and oscillations. This article provides a brief history of the junction between plasmas and plasmonics as well as highlights a few fundamental physical links.

Designing atmospheric-pressure plasma sources for surface engineering of nanomaterials

Atmospheric-pressure plasma processing techniques emerge as efficient and convenient tools to engineer a variety of nanomaterials for advanced applications in nanoscience and nanotechnology. This work presents different methods, including using a quasi-sinusoidal high-voltage generator, a radio-frequency power supply, and a uni-polar pulse generator, to generate atmospheric-pressure plasmas in the jet or dielectric barrier discharge configurations. The applicability of the atmospheric-pressure plasma is exemplified by the surface modification of nanoparticles for polymeric nanocomposites. Dielectric measurements reveal that representative nanocomposites with plasma modified nanoparticles exhibit notably higher dielectric breakdown strength and a significantly extended lifetime.

Feather-like He plasma plumes in surrounding N2 gas

Effects of surrounding gases on the propagation of room-temperature atmospheric-pressure plasma jets are reported. A highly unusual feather-like plasma plume is observed only when N2 is used as surrounding gas. The He concentration on the axis at the starting point of the feather-like plume is ∼0.85 of the maximum value and is independent on the He flow rates. High-speed optical imaging reveals that dim diffuse plasmas emerge just behind the bright head of the plasma bullet at the starting point of the feather-like plume. These results help tailoring surface exposure in emerging applications of plasma jets in medicine and nanotechnology.