335 research outputs found
Local structure of Liquid-Vapour Interfaces
The structure of a simple liquid may be characterised in terms of ground
state clusters of small numbers of atoms of that same liquid. Here we use this
sensitive structural probe to consider the effect of a liquid-vapour interface
upon the liquid structure. At higher temperatures (above around half the
critical temperature) we find that the predominant effect of the interface is
to reduce the local density, which significantly suppresses the local cluster
populations. At lower temperatures, however, pronounced interfacial layering is
found. This appears to be connected with significant orientational ordering of
clusters based on 3- and 5-membered rings, with the rings aligning
perpendicular and parallel to the interface respectively. At all temperatures,
we find that the population of five-fold symmetric structures is suppressed,
rather than enhanced, close to the interface.Comment: 10 pages, 8 figures, accepted for publication by Molecular Physic
The effect of attractions on the local structure of liquids and colloidal fluids
We revisit the role of attractions in liquids and apply these concepts to
colloidal suspensions. Two means are used to investigate the structure; the
pair correlation function and a recently developed topological method. The
latter identifies structures topologically equivalent to ground state clusters
formed by isolated groups of 5 < m < 13 particles, which are specific to the
system under consideration. Our topological methodology shows that, in the case
of Lennard-Jones, the addition of attractions increases the system's ability to
form larger (m>8) clusters, although pair-correlation functions are almost
identical. Conversely, in the case of short-ranged attractions, pair
correlation functions show a significant response to adding attraction, while
the liquid structure exhibits a strong decrease in clustering upon adding
attractions. Finally, a compressed, weakly interacting system shows a similar
pair structure and topology.Comment: 22 page
Assessment of the potential in vivo ecotoxicity of Double-Walled Carbon Nanotubes (DWNTs) in water, using the amphibian Ambystoma mexicanum
Because of their specific properties (mechanical, electrical, etc), carbon nanotubes (CNTs) are being assessed for inclusion in many manufactured products. Due to their massive production and number of potential applications, the impact of CNTs on the environment must be taken into consideration. The present investigation evaluates the ecotoxic potential of CNTs in the amphibian larvae (Ambystoma mexicanum). Acute toxicity and genotoxicity were analysed after 12 days of exposure in laboratory conditions. The genotoxic effects were analysed by scoring the micronucleated erythrocytes in the
circulating blood of the larvae according to the French standard micronucleus assay. The results obtained in the present study demonstrated that CNTs are neither acutely toxic nor genotoxic to larvae whatever the CNTs concentration in the water, although black masses of CNTs were observed inside the gut. In the increasing economical context of CNTs, complementary studies must be undertaken, especially including mechanistic and environmental investigations
Travelling and sticky affects: : Exploring teens and sexualized cyberbullying through a Butlerian-Deleuzian- Guattarian lens
In this paper we combine the thinking of Deleuze and Guattari (1984, 1987) with Judith Butler’s (1990, 1993, 2004, 2009) work to follow the rhizomatic becomings of young people’s affective relations in a range of on- and off-line school spaces. In particular we explore how events that may be designated as sexual cyberbullying are constituted and how they are mediated by technology (such as texting or in/through social networking sites). Drawing on findings from two different studies looking at teens’ uses of and experiences with social networking sites, Arto in Denmark, and Bebo in the UK, we use this approach to think about how affects flow, are distributed, and become fixed in assemblages. We map how affects are manoeuvred and potentially disrupted by young people, suggesting that in the incidences discussed affects travel as well as stick in points of fixation. We argue that we need to grasp both affective flow and fixity in order to gain knowledge of how subjectification of the gendered/classed/racialised/sexualised body emerges. A Butlerian-Deleuzian-Guattarian frame helps us to map some of these affective complexities that shape sexualized cyberbully events; and to recognize technologically mediated lines of flight when subjectifications are at least temporarily disrupted and new terms of recognition and intelligibility staked out. Keywords
Geometric frustration in small colloidal clusters
We study the structure of clusters in a model colloidal system with competing
interactions using Brownian dynamics simulations. A short-ranged attraction
drives clustering, while a weak, long-ranged repulsion is used to model
electrostatic charging in experimental systems. The former is treated with a
short-ranged Morse attractive interaction, the latter with a repulsive Yukawa
interaction. We consider the yield of clusters of specific structure as a
function of the strength of the interactions, for clusters with m=3,4,5,6,7,10
and 13 colloids. At sufficient strengths of the attractive interaction (around
10 kT), the average bond lifetime approaches the simulation timescale and the
system becomes nonergodic. For small clusters m<=5 where geometric frustration
is not relevant, despite nonergodicity, for sufficient strengths of the
attractive interaction the yield of clusters which maximise the number of bonds
approaches 100%. However for and higher, in the nonergodic regime we find
a lower yield of these structures where we argue geometric frustration plays a
significant role. is a special case, where two structures, of octahedral
and C2v symmetry compete, with the latter being favoured by entropic
contributions in the ergodic regime and by kinetic trapping in the nonergodic
regime. We believe that our results should be valid as far as the one-component
description of the interaction potential is valid. A system with competing
electrostatic repulsions and van der Waals attractions may be such an example.
However, in some cases, the one-component description of the interaction
potential may not be appropriate.Comment: 21 pages, accepted for publication by J. Phys. Condens. Matte
Opportunities for low indirect land use biomass for biofuels in Europe
Sustainable biofuels are an important tool for the decarbonisation of transport. This is especially true in aviation, maritime, and heavy-duty sectors with limited short-term alternatives. Their use by conventional transport fleets requires few changes to the existing infrastructure and engines, and thus their integration can be smooth and relatively rapid. Provision of feedstock should comply with sustainability principles for (i) producing additional biomass without distorting food and feed markets and (ii) addressing challenges for ecosystem services, including biodiversity, and soil quality. This paper performs a meta-analysis of current research for low indirect land use change (ILUC) risk biomass crops for sustainable biofuels that benefited either from improved agricultural practices or from cultivation in unused, abandoned, or severely degraded land. Two categories of biomass crops are considered here: oil and lignocellulosic. The findings confirm that there are significant opportunities to cultivate these crops in European agro-ecological zones with sustainable agronomic practices both in farming land and in land with natural constraints (unused, abandoned, and degraded land). These could produce additional low environmental impact feedstocks for biofuels and deliver economic benefits to farmer
Multiwavelength Observations of Supersonic Plasma Blob Triggered by Reconnection Generated Velocity Pulse in AR10808
Using multi-wavelength observations of Solar and Heliospheric Observatory
(SoHO)/Michelson Doppler Imager (MDI), Transition Region and Coronal Explorer
(TRACE) 171 \AA, and H from Culgoora Solar Observatory at Narrabri,
Australia, we present a unique observational signature of a propagating
supersonic plasma blob before an M6.2 class solar flare in AR10808 on 9th
September 2005. The blob was observed between 05:27 UT to 05:32 UT with almost
a constant shape for the first 2-3 minutes, and thereafter it quickly vanished
in the corona. The observed lower bound speed of the blob is estimated as
215 km s in its dynamical phase. The evidence of the blob with
almost similar shape and velocity concurrent in H and TRACE 171 \AA\
supports its formation by multi-temperature plasma. The energy release by a
recurrent 3-D reconnection process via the separator dome below the magnetic
null point, between the emerging flux and pre-existing field lines in the lower
solar atmosphere, is found to be the driver of a radial velocity pulse outwards
that accelerates this plasma blob in the solar atmosphere. In support of
identification of the possible driver of the observed eruption, we solve the
two-dimensional ideal magnetohydrodynamic equations numerically to simulate the
observed supersonic plasma blob. The numerical modelling closely match the
observed velocity, evolution of multi-temperature plasma, and quick vanishing
of the blob found in the observations. Under typical coronal conditions, such
blobs may also carry an energy flux of 7.0 ergs cm
s to re-balance the coronal losses above active regions.Comment: Solar Physics; 22 Pages; 8 Figure
Oscillations and waves in solar spicules
Since their discovery, spicules have attracted increased attention as energy/mass bridges between the dense and dynamic photosphere and the tenuous hot solar corona. Mechanical energy of photospheric random and coherent motions can be guided by magnetic field lines, spanning from the interior to the upper parts of the solar atmosphere, in the form of waves and oscillations. Since spicules are one of the most pronounced features of the chromosphere, the energy transport they participate in can be traced by the observations of their oscillatory motions. Oscillations in spicules have been observed for a long time. However the recent high-resolutions and high-cadence space and ground based facilities with superb spatial, temporal and spectral capacities brought new aspects in the research of spicule dynamics. Here we review the progress made in imaging and spectroscopic observations of waves and oscillations in spicules. The observations are accompanied by a discussion on theoretical modelling and interpretations of these oscillations. Finally, we embark on the recent developments made on the presence and role of Alfven and kink waves in spicules. We also address the extensive debate made on the Alfven versus kink waves in the context of the explanation of the observed transverse oscillations of spicule axes
- …