54,306 research outputs found
Fluids confined in wedges and by edges: From cluster integrals to thermodynamic properties referred to different regions
Recently, new insights in the relation between the geometry of the vessel
that confines a fluid and its thermodynamic properties were traced through the
study of cluster integrals for inhomogeneous fluids. In this work I analyze the
thermodynamic properties of fluids confined in wedges or by edges, emphasizing
on the question of the region to which these properties refer. In this context,
the relations between the line-thermodynamic properties referred to different
regions are derived as analytic functions of the dihedral angle , for
, which enables a unified approach to both edges and wedges. As
a simple application of these results, I analyze the properties of the confined
gas in the low-density regime. Finally, using recent analytic results for the
second cluster integral of the confined hard sphere fluid, the low density
behavior of the line thermodynamic properties is analytically studied up to
order two in the density for and by adopting different
reference regions.Comment: 8 pages, 7 figure
Efficiency of autonomous soft nano-machines at maximum power
We consider nano-sized artificial or biological machines working in steady
state enforced by imposing non-equilibrium concentrations of solutes or by
applying external forces, torques or electric fields. For unicyclic and
strongly coupled multicyclic machines, efficiency at maximum power is not
bounded by the linear response value 1/2. For strong driving, it can even
approach the thermodynamic limit 1. Quite generally, such machines fall in
three different classes characterized, respectively, as "strong and efficient",
"strong and inefficient", and "balanced". For weakly coupled multicyclic
machines, efficiency at maximum power has lost any universality even in the
linear response regime
A Reversibility Parameter for a Markovian Stepper
Recent experimental studies on the stepwize motion of biological molecular
motors have revealed that the ``characteristic distance'' of a step is usually
less than the actual step size. This observation implies that the
detailed-balance condition for kinetic rates of steps is violated in these
motors. In this letter, in order to clarify the significance of the
characteristic distance, we study a Langevin model of a molecular motor with a
hidden degree of freedom. We find that the ratio of the characteristic distance
to the step size is equal to unity if the dominant paths in the state space are
one dimensional, while it deviates from unity if the dominant paths are
branched. Therefore, this parameter can be utilized to determine the
reversibility of a motor even under a restricted observation.Comment: 6 pages, 2 figures - minor revision
Adhesive for aluminum withstands cryogenic temperatures
Polyurethane adhesive mixed to various proportions with milled glass fibers match the thermal characteristics of 2014-T6 aluminum at cryogenic temperatures
The Complete Jamming Landscape of Confined Hard Discs
An exact description of the complete jamming landscape is developed for a
system of hard discs of diameter , confined between two lines separated
by a distance . By considering all possible local
packing arrangements, the generalized ensemble partition function of jammed
states is obtained using the transfer matrix method, which allows us to
calculate the configurational entropy and the equation of state for the
packings. Exploring the relationship between structural order and packing
density, we find that the geometric frustration between local packing
environments plays an important role in determining the density distribution of
jammed states and that structural "randomness" is a non-monotonic function of
packing density. Molecular dynamics simulations show that the properties of the
equilibrium liquid are closely related to those of the landscape.Comment: 5 Pages, 4 figure
An exact formalism to study the thermodynamic properties of hard-sphere systems under spherical confinement
This paper presents a modified grand canonical ensemble which provides a new
simple and efficient scheme to study few-body fluid-like inhomogeneous systems
under confinement. The new formalism is implemented to investigate the exact
thermodynamic properties of a hard sphere (HS) fluid-like system with up to
three particles confined in a spherical cavity. In addition, the partition
function of this system was used to analyze the surface thermodynamic
properties of the many-HS system and to derive the exact curvature dependence
of both the surface tension and adsorption in powers of the density. The
expressions for the surface tension and the adsorption were also obtained for
the many- HS system outside of a fixed hard spherical object. We used these
results to derive the dependence of the fluid-substrate Tolman length up to
first order in density.Comment: 6 figures. The paper includes new exact results about hard spheres
fluid-like system
Sensing of Fluctuating Nanoscale Magnetic Fields Using NV Centres in Diamond
New magnetometry techniques based on Nitrogen-Vacancy (NV) defects in diamond
allow for the imaging of static (DC) and oscillatory (AC) nanoscopic magnetic
systems. However, these techniques require accurate knowledge and control of
the sample dynamics, and are thus limited in their ability to image fields
arising from rapidly fluctuating (FC) environments. We show here that FC fields
place restrictions on the DC field sensitivity of an NV qubit magnetometer, and
that by probing the dephasing rate of the qubit in a magnetic FC environment,
we are able to measure fluctuation rates and RMS field strengths that would be
otherwise inaccessible with the use of DC and AC magnetometry techniques. FC
sensitivities are shown to be comparable to those of AC fields, whilst
requiring no additional experimental overheads or control over the sample.Comment: 5 pages, 4 figure
Compressive force generation by a bundle of living biofilaments
To study the compressional forces exerted by a bundle of living stiff
filaments pressing on a surface, akin to the case of an actin bundle in
filopodia structures, we have performed particulate Molecular Dynamics
simulations of a grafted bundle of parallel living (self-assembling) filaments,
in chemical equilibrium with a solution of their constitutive monomers.
Equilibrium is established as these filaments, grafted at one end to a wall of
the simulation box, grow at their chemically active free end and encounter the
opposite confining wall of the simulation box. Further growth of filaments
requires bending and thus energy, which automatically limit the populations of
longer filaments. The resulting filament sizes distribution and the force
exerted by the bundle on the obstacle are analyzed for different grafting
densities and different sub- or supercritical conditions, these properties
being compared with the predictions of the corresponding ideal confined bundle
model. In this analysis, non-ideal effects due to interactions between
filaments and confinement effects are singled out. For all state points
considered at the same temperature and at the same gap width between the two
surfaces, the force per filament exerted on the opposite wall appears to be a
function of a rescaled free monomer density . This
quantity can be estimated directly from the characteristic length of the
exponential filament size distribution observed in the size domain where
these grafted filaments are not in direct contact with the wall. We also
analyze the dynamics of the filament contour length fluctuations in terms of
effective polymerization () and depolymerization () rates, where again it
is possible to disentangle non-ideal and confinement effects.Comment: 24 pages, 7 figure
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Clothing longevity perspectives: exploring consumer expectations, consumption and use
The production, distribution, use and end-of-life phases of the clothing lifecycle all have significant environmental impacts, but complete lifecycle assessment has identified that extending the active life of garments through design, use and re-use is the single most effective intervention in reducing the overall impact of the clothing industry (WRAP, 2011). In response, Government funded clothing longevity research seeks to develop and test industry-led design strategies to influence and enable consumers to keep garments in active use for longer (Cooper et al., 2014). While recent UK research has indicated significant potential to influence more sustainable consumer behaviour (Langley et al., 2013; YouGov, 2012), up-to-date qualitative research is required to discover how consumer attitudes, expectations and behaviours in relation to clothing lifetimes affects garment care and clothing use. This will help to inform industry-led strategies by understanding where effective changes can be made that will potentially have most impact. This paper presents preliminary findings from a Defra funded action based research project, ‘Strategies to improve design and testing for clothing longevity’. Qualitative research methods are used to explore consumer attitudes, expectations and behaviours at purchase, use and disposal stages of garment lifetimes, and gather data on practices of garment wash, wear, care and maintenance in everyday life. The research findings are discussed in relation to industry-led strategies aimed at extending the life of clothes
Fluids confined in wedges and by edges: Virial series for the line-thermodynamic properties of hard spheres
This work is devoted to analyze the relation between the thermodynamic properties of a confined fluid and the shape of its confining vessel. Recently, new insights in this topic were found through the study of cluster integrals for inhomogeneous fluids that revealed the dependence on the vessel shape of the low density behavior of the system. Here, the statistical mechanics and thermodynamics of fluids confined in wedges or by edges is revisited, focusing on their cluster integrals. In particular, the well known hard sphere fluid, which was not studied in this framework so far, is analyzed under confinement and its thermodynamic properties are analytically studied up to order two in the density. Furthermore, the analysis is extended to the confinement produced by a corrugated wall. These results rely on the obtained analytic expression for the second cluster integral of the confined hard sphere system as a function of the opening dihedral angle 0 < β < 2π. It enables a unified approach to both wedges and edges.Fil: Urrutia, Ignacio. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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