14,562 research outputs found
Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations
Climate models simulate a strong land-ocean contrast in the response of
near-surface relative humidity to global warming: relative humidity tends to
increase slightly over oceans but decrease substantially over land. Surface
energy balance arguments have been used to understand the response over ocean
but are difficult to apply over more complex land surfaces. Here, a conceptual
box model is introduced, involving moisture transport between the land and
ocean boundary layers and evapotranspiration, to investigate the decreases in
land relative humidity as the climate warms. The box model is applied to
idealized and full-complexity (CMIP5) general circulation model simulations,
and it is found to capture many of the features of the simulated changes in
land relative humidity. The box model suggests there is a strong link between
fractional changes in specific humidity over land and ocean, and the greater
warming over land than ocean then implies a decrease in land relative humidity.
Evapotranspiration is of secondary importance for the increase in specific
humidity over land, but it matters more for the decrease in relative humidity.
Further analysis shows there is a strong feedback between changes in
surface-air temperature and relative humidity, and this can amplify the
influence on relative humidity of factors such as stomatal conductance and soil
moisture.Comment: Submitted to Journal of Climate on May 1st, 201
Supporting development for the preliminary design of an intermediate water recovery system
Supporting development of experimental design for water recovery syste
A theoretical investigation of the effect of proliferation & adhesion on monoclonal conversion in the colonic crypt
The surface epithelium lining the intestinal tract renews itself rapidly by a coordinated programme of cell proliferation, migration and differentiation events that is initiated in the crypts of Lieberkühn. It is generally believed that colorectal cancer arises due to mutations that disrupt the normal cellular dynamics of the crypts. Using a spatially structured cell-based model of a colonic crypt, we investigate the likelihood that the progeny of a mutated cell will dominate, or be sloughed out of, a crypt. Our approach is to perform multiple simulations, varying the spatial location of the initial mutation, and the proliferative and adhesive properties of the mutant cells, to obtain statistical distributions for the probability of their domination. Our simulations lead us to make a number of predictions. The process of monoclonal conversion always occurs, and does not require that the cell which initially gave rise to the population remains in the crypt. Mutations occurring more than one to two cells from the base of the crypt are unlikely to become the dominant clone. The probability of a mutant clone persisting in the crypt is sensitive to dysregulation of adhesion. By comparing simulation results with those from a simple one-dimensional stochastic model of population dynamics at the base of the crypt, we infer that this sensitivity is due to direct competition between wild-type and mutant cells at the base of the crypt. We also predict that increases in the extent of the spatial domain in which the mutant cells proliferate can give rise to counter-intuitive, non-linear changes to the probability of their fixation, due to effects that cannot be captured in simpler models
A theoretical investigation of the effect of proliferation and\ud adhesion on monoclonal conversion in the colonic crypt
Colorectal cancers are initiated by the accumulation of mutations in the colonic epithelium. Using a spatially structured cell-based model of a colonic crypt, we investigate the likelihood that the progeny of a mutated cell will dominate, or be sloughed out of, a crypt. Our approach is to perform multiple simulations, varying the spatial location of the initial mutation, and its proliferative and adhesive properties, to obtain statistical distributions for the probability of domination. Our simulations lead us to make a number of predictions. The process of monoclonal conversion always occurs, and does not require that the cell which initially gave rise to the population remains in the crypt. Mutations occurring more than one to two cells from the base of the crypt are unlikely to become the dominant clone. The probability of a mutant clone persisting in the crypt is sensitive to dysregulation of adhesion, and comparison with a one-dimensional model suggests that this is caused by competition directly at the base of the crypt.\ud
We also predict that increases in the extent of the spatial domain in which the mutant cells proliferate cause counter-intuitive non-linear changes to the probability of its fixation, due to effects that cannot be captured in simpler models
The effect of personality on collaborative task performance and interaction
Collocated, multi-user technologies, which support group-work are becoming increasingly popular. Examples include MERL's Diamondtouch and Microsoft's Surface, both of which have evolved from research prototypes to commercial products. Many applications have been developed for such technologies which support the work and entertainment needs of small groups of people. None of these applications however, have been studied in terms of the interactions and performances of their users with regards to their personality. In this paper, we address this research gap by conducting a series of user studies involving dyads working on a number of multi-user applications on the DiamondTouch tabletop device
Object-Oriented Paradigms for Modelling Vascular\ud Tumour Growth: a Case Study
Motivated by a family of related hybrid multiscale models, we have built an object-oriented framework for developing and implementing multiscale models of vascular tumour growth. The models are implemented in our framework as a case study to highlight how object-oriented programming techniques and good object-oriented design may be used effectively to develop hybrid multiscale models of vascular tumour growth. The intention is that this paper will serve as a useful reference for researchers modelling complex biological systems and that these researchers will employ some of the techniques presented herein in their own projects
Nanoscale density fluctuations in swift heavy ion irradiated amorphous SiO2
We report on the observation of nanoscale density fluctuations in 2 μm thick amorphous SiO₂ layers irradiated with 185 MeV Au ions. At high fluences, in excess of approximately 5 × 10¹² ions/cm², where the surface is completely covered by ion tracks, synchrotron small angle x-ray scattering measurements reveal the existence of a steady state of density fluctuations. In agreement with molecular dynamics simulations, this steady state is consistent with an ion track “annihilation” process, where high-density regions generated in the periphery of new tracks fill in low-density regions located at the center of existing tracks.The authors acknowledge the Australian Research
Council and the Australian Synchrotron Research Program
for financial support and thank the staff at the ANU Heavy
Ion facility for their continued technical assistance. O.P.,
F.D., and K.N. acknowledge financial support from the
Academy of Finland under its Centre of Excellence program
as well as the OPNA project, and grants of computer
capacity from CSC
The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems
We investigate the relationship between age and chromospheric activity for
139 M dwarf stars in wide binary systems with white dwarf companions. The age
of each system is determined from the cooling age of its white dwarf component.
The current limit for activity-age relations found for M dwarfs in open
clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for
the exploration of this relationship at ages older than 4 Gyr. The general
trend of stars remaining active for a longer time at later spectral type is
confirmed. However, our larger sample and greater age range reveals additional
complexity in assigning age based on activity alone. We find that M dwarfs in
wide binaries older than 4 Gyr depart from the log-linear relation for clusters
and are found to have activity at magnitudes, colors and masses which are
brighter, bluer and more massive than predicted by the cluster relation. In
addition to our activity-age results, we present the measured radial velocities
and complete space motions for 161 white dwarf stars in wide binaries.Comment: 22 pages including 9 figures and 5 tables. Accepted for publication
in The Astronomical Journa
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