Onset of the magnetized arc and its effect on the momentum of a low-power two-stage pulsed magneto-plasma-dynamic thruster

A new type of plasma accelerator-a low-power (<30W), miniature (cm-sized), two-stage pulsed magneto-plasma-dynamic thruster-has been proposed. Being magnetized by an axially symmetric dc magnetic field of ∼200 mT, the vacuum arc discharge demonstrates a threshold behavior: Parameters such as thrust and the thrust-to-power ratio rapidly jump after a certain dc voltage (∼30 V) is applied on the accelerating electrode. We show that such an effect improves the thrust (from ∼2 to ∼210 µN), efficiency (from ∼1% to 50%), and thrust-to-power ratio (from ∼0.5 to ∼18 µN/W).

Recent progress and perspectives of space electric propulsion systems based on smart nanomaterials

Drastic miniaturization of electronics and ingression of next-generation nanomaterials into space technology have provoked a renaissance in interplanetary flights and near-Earth space exploration using small unmanned satellites and systems. As the next stage, the NASA's 2015 Nanotechnology Roadmap initiative called for new design paradigms that integrate nanotechnology and conceptually new materials to build advanced, deep-space-capable, adaptive spacecraft. This review examines the cutting edge and discusses the opportunities for integration of nanomaterials into the most advanced types of electric propulsion devices that take advantage of their unique features and boost their efficiency and service life. Finally, we propose a concept of an adaptive thruster.

Substrate independent approach for synthesis of graphene platelet networks

Graphene platelet networks (GPNs) comprised of randomly oriented graphene flakes two to three atomic layers thick are synthesized using a novel plasma-based approach. The approach uses a substrate capable of withstanding synthesis temperatures around 800 °C, but is fully independent of the substrate material. The synthesis occurs directly on the substrate surface without the necessity of any additional steps. GPNs were synthesized on various substrate materials including silicon (Si), thermally oxidized Si (SiO₂), molybdenum (Mo), nickel (Ni) and copper (Cu), nickel-chromium (NiCr) alloy and alumina ceramics (Al₂O₃). The mismatch between the atomic structures of sp² honeycomb carbon networks and the substrate material is fully eliminated shortly after the synthesis initiation, namely when about 100 nm thick deposits are formed on the substrate. GPN structures synthesized on a substrate at a temperature of about 800 °C are significantly more porous in comparison to the much denser packed amorphous carbon deposits synthesized at lower temperatures. The method proposed here can potentially revolutionize the area of electrochemical energy storage by offering a single-step direct approach for the manufacture of graphene-based electrodes for non-Faradaic supercapacitors. Mass production can be achieved using this method if a roll-to-roll system is utilized.

Self-organized graphene-like boron nitride containing nanoflakes on copper by low-temperature N2 + H2 plasma

A simple and efficient method for synthesizing complex graphene-inspired BNCO nanoflakes by plasma-enhanced hot filament chemical vapour deposition using B₄C as a precursor and N₂/H₂ reactive gases is reported.

Measurements of streamer head potential and conductivity of streamer column in the cold nonequilibrium atmospheric plasmas

This work presents a simple method for the characterization of streamers developing in cold atmospheric plasma jets. The method is based upon stopping ("scattering") of streamer by means of external DC potential in order to determine the potential of the streamer head. The experimental evidence presented in this work does not support the model of the electrically insulated streamer head. On the contrary, it is shown that the electrode potential is transferred to the streamer head along the streamer column to which it is attached with no significant voltage drop. Based on the proposed method, we determine various streamer parameters such as head charge (1-2×108 electrons), electrical field in the head vicinity (about 100 kV/cm), average conductivity (10-2 Ω-1cm-1) and plasma density of the streamer column (2×1013 cm-3).

Cold plasma selectivity and the possibility of a paradigm shift in cancer therapy

Background:

Plasma is an ionised gas that is typically generated in high-temperature laboratory conditions. However, recent progress in atmospheric plasmas has led to the creation of cold plasmas with ion temperature close to room temperature.

Methods:

Both in-vitro and in-vivo studies revealed that cold plasmas selectively kill cancer cells.

Results:

We show that: (a) cold plasma application selectively eradicates cancer cells in vitro without damaging normal cells; and (b) significantly reduces tumour size in vivo. It is shown that reactive oxygen species metabolism and oxidative stress responsive genes are deregulated.

Conclusion:

The development of cold plasma tumour ablation has the potential of shifting the current paradigm of cancer treatment and enabling the transformation of cancer treatment technologies by utilisation of another state of matter.

Single-step synthesis and magnetic separation of graphene and carbon nanotubes in arc discharge plasmas

The unique properties of graphene and carbon nanotubes made them the most promising nanomaterials attracting enormous attention, due to the prospects for applications in various nanodevices, from nanoelectronics to sensors and energy conversion devices. Here we report on a novel deterministic, single-step approach to simultaneous production and magnetic separation of graphene flakes and carbon nanotubes in an arc discharge by splitting the high-temperature growth and low-temperature separation zones using a non-uniform magnetic field and tailor-designed catalyst alloy, and depositing nanotubes and graphene in different areas. Our results are very relevant to the development of commercially-viable, single-step production of bulk amounts of high-quality graphene.

Ignition and temperature behavior of a single-wall carbon nanotube sample

The electrical resistance of mats of single-wall carbon nanotubes (SWNTs) is measured as a function of mat temperature under various helium pressures, in vacuum and in atmospheric air. The objective of this paper is to study the thermal stability of SWNTs produced in a helium arc discharge in the experimental conditions close to natural conditions of SWNT growth in an arc, using a furnace instead of an arc discharge. For each tested condition, there is a temperature threshold at which the mat's resistance reaches its minimum. The threshold value depends on the helium pressure. An increase of the temperature above the temperature threshold leads to the destruction of SWNT bundles at a certain critical temperature. For instance, the critical temperature is about 1100 K in the case of helium background at a pressure of about 500 Torr. Based on experimental data on critical temperature it is suggested that SWNTs produced by an anodic arc discharge and collected in the web area outside the arc plasma most likely originate from the arc discharge peripheral region.

Prior use of statins and outcome in patients with intracerebral haemorrhage

BACKGROUND

Pre-treatment with cholesterol lowering drugs of the statin family may exert protective effects in patients with ischaemic stroke and subarachnoid haemorrhage but their effects are not clear in patients with intracerebral haemorrhage (ICH).

METHODS

We recruited patients admitted to our University Hospital with an acute ICH and analysed pre-admission demographic variables, pre-morbid therapy, clinical and radiological prognostic markers and outcome variables including 90-day modified Rankin score and NIH stroke scale score (NIHSS).

RESULTS

We recruited 399 patients with ICH of which 101 (25%) were using statins. Statin users more often had vascular risk factors, had significantly lower haematoma volumes (P = 0.04) and had lower mortality rates compared with non-users (45.6% vs. 56.1%; P = 0.11). However, statin treatment did not have a statistically significant impact on mortality or functional outcome on multiple logistic regression analysis.

CONCLUSIONS

Treatment with statins prior to ICH failed to show a significant impact on outcome in this analysis despite lower haematoma volumes.

Plasma-assembled carbon nanotubes: electric field-related effects

The paper presents results of comparative investigation of carbon nanotubes growth processes in dense low-temperature plasma and on substrate surface. Hybrid/Monte-Carlo numerical simulations were used to demonstrate the differences in the ion fluxes, growth rates and kinetics of adsorbed atoms re-distribution on substrate and nanotubes surfaces. We show that the plasma parameters significantly affect the nanotubes growth kinetics. We demonstrate that the growth rates of the nanotubes in plasma and on surface can differ by three orders, and the specific fluxes to the nanotube in the plasma can exceed the flux to surface-grown nanotube by six orders. We also show that the metal catalyst used for the nanotubes production on surface and in arc is a subject to very different conditions and this may be a key factor for the nanotube growth mode. The obtained dependencies for the ion fluxes to the nanotubes and nanotubes growth rates on the plasma parameters may be useful for selection of the production methods.

Modeling of the anodic arc discharge and conditions for single-wall carbon nanotube growth

A model of the arc discharge used for a single wall carbon nanotube (SWNT) synthesis is developed. Coupling solution of the non-equilibrium, Knudsen layer, with hydrodynamic layer and discharge column provides self-consistent solution for the ablation rate and plasma parameter distribution. It is predicted that the interelectrode gap decreases with the background pressure increase. Conditions for single wall carbon nanotube formation in the arc discharge method of nanotube synthesis are described. Carbon nanotube seed formation and charging in the interelectrode gap are found to be very important effects that may alter carbon nanotube formation in the cathode region. This model predicts that the long carbon nanotubes in the high pressure Helium environment can be deposited on the cathode surface. Model predictions are found to be in agreement with experiment.