1,749 research outputs found
Superhydrophobicity on hairy surfaces
We investigate the wetting properties of surfaces patterned with fine elastic
hairs, with an emphasis on identifying superhydrophobic states on hydrophilic
hairs. We formulate a two dimensional model of a large drop in contact with a
row of equispaced elastic hairs and, by minimising the free energy of the
model, identify the stable and metastable states. In particular we concentrate
on "partially suspended" states, where the hairs bend to support the drop --
singlet states where all hairs bend in the same direction, and doublet states
where neighbouring hairs bend in opposite directions -- and find the limits of
stability of these configurations in terms of material contact angle, hair
flexibility, and system geometry. The drop can remain suspended in a singlet
state at hydrophilic contact angles, but doublets exist only when the hairs are
hydrophobic. The system is more likely to evolve into a singlet state if the
hairs are inclined at the root. We discuss how, under limited circumstances,
the results can be modified to describe an array of hairs in three dimensions.
We find that now both singlets and doublets can exhibit superhydrophobic
behaviour on hydrophilic hairs. We discuss the limitations of our approach and
the directions for future work
Nonparametric methods for the characteristic model
Characteristics models have been found to be useful in many areas of
economics. However, their empirical implementation tends to rely heavily
on functional form assumptions. In this paper we develop a revealed
preference-based nonparametric approach to characteristics models. We
derive the minimal necessary and sufficient empirical conditions under
which data on the market behaviour of individual, heterogeneous, pricetaking
consumers are nonparametrically consistent with the consumer
characteristics model. Where these conditions hold, we show how information
may be recovered on individual consumer’s marginal valuations
of product attributes. In some cases marginal valuations are point identified
and in other cases we can only recover bounds. Where the conditions
fail we highlight the role which the introduction of unobserved product
attributes can play in rationalising the data. We implement these ideas
using consumer panel data on the Danish milk market
A nonparametric characteristics model of the demand for milk
Characteristics models in demand analysis capture the idea that people value goods not For the commodity itself but for the characteristics (or attributes) or embodied in the good. For example, agents may care about the fat content and the taste of different sorts of milk but not the actual type of milk. When we have fewer characteristics than types of good the theory imposes restrictions on observables. We present a revealed preference characteristics model analysis of the demand for milk in Denmark
Biphasic, Lyotropic, Active Nematics
We perform dynamical simulations of a two-dimensional active nematic fluid in
coexistence with an isotropic fluid. Drops of active nematic become elongated,
and an effective anchoring develops at the nematic-isotropic interface. The
activity also causes an undulatory instability of the interface. This results
in defects of positive topological charge being ejected into the nematic,
leaving the interface with a diffuse negative charge. Quenching the active
lyotropic fluid results in a steady state in which phase-separating domains are
elongated and then torn apart by active stirring.Comment: 7 pages, 8 figure
On the Simultaneous Perception of Sound and Three-Dimensional Objects
Although examples of work investigating the perceptual relationship and possibilities of sound and image are common, relatively litle work has been carried out into multimedia works combining sound and three-dimensional objects. A practice-based investigation into this subject is presented with original artworks and contectual material from sound art, sculpture, moving image and psychology. The project sets out to more examine the perception of multimedia work, specifically through the creation and analysis of artworks combining sound and physical objects. It considers three main areas of study: sound’s ability to draw attention to, or modify, the existing properties of an object; techniques which encourage sound and object to appear cohesively as part of the same work; and a discussion of cognitive effects that may occur as a result of their simulataneous perception. Using the concept of the search space from evolutionary computing as an example, the case is made that multimedia artworksde
can present a larger field of creative opportunity than single-media works, due to the enhanced interplay between the two media and the viewer's a priori knowledge. The roles of balance, dynamism and interactivity in multimedia work are also explored. Throughout the thesis examples of original artworks are given which exemplify the issues raised. The main outcome of the study is a proposed framework
for categorising and analysing the perception of multimedia artworks, based on increasing semantic
separation between the sensory elements. It is claimed that as the relationship between these elements becomes less obvious, more work is demanded of the viewer's imagination in trying to reconcile the gap,
leading to active engagement and the possibility of extra imaginary forms which do not exist in the original material. It is proposed that the framework and ideas in this document will be applicable beyond the sound/object focus of this study, and it is hoped they will inform research into multimedia work in other forms
3 tera-basepairs as a fundamental limit for robust DNA replication
10 p.-2 tab.In order to maintain functional robustness and species integrity, organisms must ensure high fidelity of the genome duplication process. This is particularly true during early development, where cell division is often occurring both rapidly and coherently. By studying the extreme limits of suppressing DNA replication failure due to double fork stall errors, we uncover a fundamental constant that describes a trade-off between genome size and architectural complexity of the developing organism. This constant has the approximate value N_U ≈ 3×10^12 basepairs, and depends only on two highly conserved molecular properties of DNA biology. We show that our theory is successful in interpreting a diverse range of data across the Eukaryota.MAM, LA and TJN acknowledge prior support from the Scottish Universities Life Sciences Alliance. JJB acknowledges support from Cancer Research UK (grant C303/A14301) and the Wellcome Trust (grant WT096598MA). TJN acknowledges prior support from the National Institutes of Health (Physical Sciences in Oncology Centers, U54 CA143682).Peer reviewe
Functional genomics of a symbiotic community : shared traits in the olive fruit fly gut microbiota
The olive fruit fly Bactrocera oleae is a major pest of olives worldwide and houses a specialized gut microbiota dominated by the obligate symbiont “Candidatus Erwinia dacicola”. Ca. E. dacicola is thought to supplement dietary nitrogen to the host, with only indirect evidence for this hypothesis so far. Here, we sought to investigate the contribution of the symbiosis to insect fitness and explore the ecology of the insect gut. For this purpose, we examined the composition of bacterial communities associated with Cretan olive fruit fly populations, and inspected several genomes and one transcriptome assembly. We identified, and reconstructed the genome of, a novel component of the gut microbiota, Tatumella sp. TA1, which is stably associated with Mediterranean olive fruit fly populations. We also reconstructed a number of pathways related to nitrogen assimilation and interactions with the host. The results show that, despite variation in taxa composition of the gut microbial community, core functions related to the symbiosis are maintained. Functional redundancy between different microbial taxa was observed for genes involved in urea hydrolysis. The latter is encoded in the obligate symbiont genome by a conserved urease operon, likely acquired by horizontal gene transfer, based on phylogenetic evidence. A potential underlying mechanism is the action of mobile elements, especially abundant in the Ca. E. dacicola genome. This finding, along with the identification, in the studied genomes, of extracellular surface structure components that may mediate interactions within the gut community, suggest that ongoing and past genetic exchanges between microbes may have shaped the symbiosis
Design of fast core node processor for packet forwarding without header modification in optical networks
We present a design of a fast all-optical core-node processor that performs packet-forwarding in optical networks without header-modification. The design is based on bit-serial architecture using TOADs as logic-gates that perform modulo-arithmetic to forward packets
Upgrading legacy long-haul WDM systems through unbalancing the proportion of 1s and 0s in the transmitted data
We present experimental results for wavelength-division multiplexed (WDM) transmission performance using unbalanced proportions of 1s and 0s in pseudo-random bit sequence (PRBS) data. This investigation simulates the effect of local, in time, data unbalancing which occurs in some coding systems such as forward error correction when extra bits are added to the WDM data stream. We show that such local unbalancing, which would practically give a time-dependent error-rate, can be employed to improve the legacy long-haul WDM system performance if the system is allowed to operate in the nonlinear power region. We use a recirculating loop to simulate a long-haul fibre system
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