408 research outputs found
Tolerance of Artemia to static and shock pressure loading
Hydrostatic and hydrodynamic pressure loading has been applied to unicellular organisms for a number of years due to interest from food technology and extremophile communities. There is also an emerging interest in the response of multicellular organisms to high pressure conditions. Artemia salina is one such organism. Previous experiments have shown a marked difference in the hatching rate of these organisms after exposure to different magnitudes of pressure, with hydrostatic tests showing hatching rates at pressures up to several GPa, compared to dynamic loading that resulted in comparatively low survival rates at lower pressure magnitudes. In order to begin to investigate the origin of this difference, the work presented here has focussed on the response of Artemia salina to (quasi) one-dimensional shock loading. Such experiments were carried out using the plate-impact technique in order to create a planar shock front. Artemia cysts were investigated in this manner along with freshly hatched larvae (nauplii). The nauplii and cysts were observed post-shock using optical microscopy to detect motility or hatching, respectively. Hatching rates of 18% were recorded at pressures reaching 1.5 GPa, as determined with the aid of numerical models. Subjecting Artemia to quasi-one-dimensional shock loading offers a way to more thoroughly explore the shock pressure ranges these organisms can survive
On the response of Escherichia coli to high rates of deformation
While a large body of work exists on the low strain-rate loading of biological systems such as bacteria, there is a paucity of information on the response of such organisms at high rates of deformation. Here, the response of a readily accessible strain of bacteria, Escherichia coli (E. coli), has been examined under shock loading conditions. Although previous studies have shown greatly reduced growth in shock conditions up to several GPa, relationships between loading conditions and bacterial response have yet to be fully elucidated. Initial results of a more rigorous investigation into the 1D shock loading response of E. coli are presented here, expectantly leading to a more comprehensive view of its behaviour when exposed to high pressures. Comparison has been drawn to provide insight into the importance of the nature of the loading regime to the survival of these biological systems
Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domains
By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth
A picogram and nanometer scale photonic crystal opto-mechanical cavity
We describe the design, fabrication, and measurement of a cavity
opto-mechanical system consisting of two nanobeams of silicon nitride in the
near-field of each other, forming a so-called "zipper" cavity. A photonic
crystal patterning is applied to the nanobeams to localize optical and
mechanical energy to the same cubic-micron-scale volume. The picrogram-scale
mass of the structure, along with the strong per-photon optical gradient force,
results in a giant optical spring effect. In addition, a novel damping regime
is explored in which the small heat capacity of the zipper cavity results in
blue-detuned opto-mechanical damping.Comment: 15 pages, 4 figure
Exploring the science–policy interface on climate change: The role of the IPCC in informing local decision-making in the UK
Building on the Intergovernmental Panel on Climate Change’s (IPCC) review of
how to make its Assessment Reports (ARs) more accessible in the future, the research
reported here assesses the extent to which the ARs are a useful tool through which scientific
advice informs local decision-making on climate change in the United Kingdom. Results from
interviews with local policy representatives and three workshops with UK academics, practitioners
and local decision makers are presented. Drawing on these data, we outline three
key recommendations made by participants on how the IPCC ARs can be better utilized as a
form of scientific advice to inform local decision-making on climate change. First, to provide
more succinct summaries of the reports paying close attention to the language, content,
clarity, context and length of these summaries; second, to better target and frame the reports
from a local perspective to maximize engagement with local stakeholders; and third, to work
with local decision makers to better understand how scientific advice on climate change is
being incorporated in local decision-making. By adopting these, the IPCC would facilitate local
decision-making on climate change and provide a systematic review of how its reports are
being used locally. We discuss implications of these recommendations and their relevance to
the wider debate within and outside the IPCC as to the most effective way the IPCC can more
effectively tailor its products to user needs without endangering the robustness of its scientific
findings. This article is published as part of a collection on scientific advice to government
Baubles, Bangles, and Biotypes: A Critical Review of the use and Abuse of the Biotype Concept
Pest species of insects are notoriously prone to escape the weapons deployed in management efforts against them. This is particularly true in herbivorous insects. When a previously successful tactic fails the insect population has apparently adapted to it and is often considered to be a new or distinct entity, and given the non-formal category ‘biotype’. The entities falling under the umbrella term ‘biotype’ are not consistent either within or between biotypes, and their underlying genetic composition and origins, while generally unknown, are likely heterogeneous within and variable between biotypes. In some cases race or species may be more appropriate referents. Some examples of applications of the concept in the context of host plant resistance are discussed. It is argued here that the term ‘biotype’ and its applications are overly simplistic, confused, have not proved useful in current pest management, and lack predictive power for future management
Laser cooling of a nanomechanical oscillator into its quantum ground state
A patterned Si nanobeam is formed which supports co-localized acoustic and
optical resonances that are coupled via radiation pressure. Starting from a
bath temperature of T=20K, the 3.68GHz nanomechanical mode is cooled into its
quantum mechanical ground state utilizing optical radiation pressure. The
mechanical mode displacement fluctuations, imprinted on the transmitted cooling
laser beam, indicate that a final phonon mode occupancy of 0.85 +-0.04 is
obtained.Comment: 18 pages, 10 figure
Cell-scale degradation of peritumoural extracellular matrix fibre network and its role within tissue-scale cancer invasion
Local cancer invasion of tissue is a complex, multiscale process which plays
an essential role in tumour progression. Occurring over many different temporal
and spatial scales, the first stage of invasion is the secretion of matrix
degrading enzymes (MDEs) by the cancer cells that consequently degrade the
surrounding extracellular matrix (ECM). This process is vital for creating
space in which the cancer cells can progress and it is driven by the activities
of specific matrix metalloproteinases (MMPs). In this paper, we consider the
key role of two MMPs by developing further the novel two-part multiscale model
introduced in [33] to better relate at micro-scale the two micro-scale
activities that were considered there, namely, the micro-dynamics concerning
the continuous rearrangement of the naturally oriented ECM fibres within the
bulk of the tumour and MDEs proteolytic micro-dynamics that take place in an
appropriate cell-scale neighbourhood of the tumour boundary. Focussing
primarily on the activities of the membrane-tethered MT1-MMP and the soluble
MMP-2 with the fibrous ECM phase, in this work we investigate the MT1-MMP/MMP-2
cascade and its overall effect on tumour progression. To that end, we will
propose a new multiscale modelling framework by considering the degradation of
the ECM fibres not only to take place at macro-scale in the bulk of the tumour
but also explicitly in the micro-scale neighbourhood of the tumour interface as
a consequence of the interactions with molecular fluxes of MDEs that exercise
their spatial dynamics at the invasive edge of the tumour
Spatio-temporal Models of Lymphangiogenesis in Wound Healing
Several studies suggest that one possible cause of impaired wound healing is
failed or insufficient lymphangiogenesis, that is the formation of new
lymphatic capillaries. Although many mathematical models have been developed to
describe the formation of blood capillaries (angiogenesis), very few have been
proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a
markedly different process from angiogenesis, occurring at different times and
in response to different chemical stimuli. Two main hypotheses have been
proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the
edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic
endothelial cells first pool in the wound region following the lymph flow and
then, once sufficiently populated, start to form a network. Here we present two
PDE models describing lymphangiogenesis according to these two different
hypotheses. Further, we include the effect of advection due to interstitial
flow and lymph flow coming from open capillaries. The variables represent
different cell densities and growth factor concentrations, and where possible
the parameters are estimated from biological data. The models are then solved
numerically and the results are compared with the available biological
literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total
Sharing vocabularies: towards horizontal alignment of values-driven business functions
This paper highlights the emergence of different ‘vocabularies’ that describe various values-driven business functions within large organisations and argues for improved horizontal alignment between them. We investigate two established functions that have long-standing organisational histories: Ethics and Compliance (E&C) and Corporate Social Responsibility (CSR). By drawing upon research on organisational alignment, we explain both the need for and the potential benefit of greater alignment between these values-driven functions. We then examine the structural and socio-cultural dimensions of organisational systems through which E&C and CSR horizontal alignment can be coordinated to improve synergies, address tensions, and generate insight to inform future research and practice in the field of Business and Society. The paper concludes with research questions that can inform future scholarly research and a practical model to guide organizations’ efforts towards inter-functional, horizontal alignment of values-driven organizational practice
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