3,120 research outputs found
The role of initial geometry in experimental models of wound closing
Wound healing assays are commonly used to study how populations of cells,
initialised on a two-dimensional surface, act to close an artificial wound
space. While real wounds have different shapes, standard wound healing assays
often deal with just one simple wound shape, and it is unclear whether varying
the wound shape might impact how we interpret results from these experiments.
In this work, we describe a new kind of wound healing assay, called a sticker
assay, that allows us to examine the role of wound shape in a series of wound
healing assays performed with fibroblast cells. In particular, we show how to
use the sticker assay to examine wound healing with square, circular and
triangular shaped wounds. We take a standard approach and report measurements
of the size of the wound as a function of time. This shows that the rate of
wound closure depends on the initial wound shape. This result is interesting
because the only aspect of the assay that we change is the initial wound shape,
and the reason for the different rate of wound closure is unclear. To provide
more insight into the experimental observations we describe our results
quantitatively by calibrating a mathematical model, describing the relevant
transport phenomena, to match our experimental data. Overall, our results
suggest that the rates of cell motility and cell proliferation from different
initial wound shapes are approximately the same, implying that the differences
we observe in the wound closure rate are consistent with a fairly typical
mathematical model of wound healing. Our results imply that parameter estimates
obtained from an experiment performed with one particular wound shape could be
used to describe an experiment performed with a different shape. This
fundamental result is important because this assumption is often invoked, but
never tested
Next-generation acceleration and code optimization for light transport in turbid media using GPUs
A highly optimized Monte Carlo (MC) code package for simulating light
transport is developed on the latest graphics processing unit (GPU) built
for general-purpose computing from NVIDIA - the Fermi GPU. In biomedical
optics, the MC method is the gold standard approach for simulating light
transport in biological tissue, both due to its accuracy and its flexibility
in modelling realistic, heterogeneous tissue geometry in 3-D. However, the
widespread use of MC simulations in inverse problems, such as treatment
planning for PDT, is limited by their long computation time. Despite its
parallel nature, optimizing MC code on the GPU has been shown to be a
challenge, particularly when the sharing of simulation result matrices among
many parallel threads demands the frequent use of atomic instructions to
access the slow GPU global memory. This paper proposes an optimization
scheme that utilizes the fast shared memory to resolve the performance
bottleneck caused by atomic access, and discusses numerous other
optimization techniques needed to harness the full potential of the GPU.
Using these techniques, a widely accepted MC code package in biophotonics,
called MCML, was successfully accelerated on a Fermi GPU by approximately
600x compared to a state-of-the-art Intel Core i7 CPU. A skin model
consisting of 7 layers was used as the standard simulation geometry. To
demonstrate the possibility of GPU cluster computing, the same GPU code was
executed on four GPUs, showing a linear improvement in performance with an
increasing number of GPUs. The GPU-based MCML code package, named GPU-MCML,
is compatible with a wide range of graphics cards and is released as an
open-source software in two versions: an optimized version tuned for high
performance and a simplified version for beginners (http://code.google.com/p/gpumcml)
Gas distribution, kinematics and star formation in faint dwarf galaxies
We compare the gas distribution, kinematics and the current star formation in
a sample of 10 very faint (-13.37 < M_B < -9.55) dwarf galaxies. For 5 of these
galaxies we present fresh, high sensitivity, GMRT HI 21cm observations. For all
our galaxies we construct maps of the HI column density at a constant linear
resolution of ~300 pc; this forms an excellent data set to check for the
presence of a threshold column density for star formation. We find that while
current star formation (as traced by Halpha emission) is confined to regions
with relatively large (N_HI > (0.4 -1.7) X 10^{21} atoms cm^{-2}) HI column
density, the morphology of the Halpha emission is in general not correlated
with that of the high HI column density gas. Thus, while high column density
gas may be necessary for star formation, in this sample at least, it is not
sufficient to ensure that star formation does in fact occur. We examine the
line profiles of the HI emission, but do not find a simple relation between
regions with complex line profiles and those with on-going star formation.
Finally, we examine the very fine scale (~20-100 pc) distribution of the HI
gas, and find that at these scales the emission exhibits a variety of shell
like, clumpy and filamentary features. The Halpha emission is sometimes
associated with high density HI clumps, sometimes the Halpha emission lies
inside a high density shell, and sometimes there is no correspondence between
the Halpha emission and the HI clumps. In summary, the interplay between star
formation and gas density in these galaxy does not seem to show the simple
large scale patterns observed in brighter galaxies (abridged).Comment: 15 pages, 6 tables, 13 figures. Accepted for publication in MNRA
A Spitzer Space Telescope survey of massive young stellar objects in the G333.2-0.4 giant molecular cloud
The G333 giant molecular cloud contains a few star clusters and H II regions,
plus a number of condensations currently forming stars. We have mapped 13 of
these sources with the appearance of young stellar objects (YSOs) with the
Spitzer Infrared Spectrograph in the SL, SH, and LH modules (5-36 micron). We
use these spectra plus available photometry and images to characterize the
YSOs. The spectral energy distributions (SEDs) of all sources peak between 35
and 110 micron, thereby showing their young age. The objects are divided into
two groups: YSOs associated with extended emission in IRAC band 2 at 4.5 micron
(`outflow sources') and YSOs that have extended emission in all IRAC bands
peaking at the longest wavelengths (`red sources'). The two groups of objects
have distinctly different spectra: All the YSOs associated with outflows show
evidence of massive envelopes surrounding the protostar because the spectra
show deep silicate absorption features and absorption by ices at 6.0, 6.8, and
15.2 micron. We identify these YSOs with massive envelopes cool enough to
contain ice-coated grains as the `bloated' protostars in the models of Hosokawa
et al. All spectral maps show ionized forbidden lines and PAH emission
features. For four of the red sources, these lines are concentrated to the
centres of the maps, from which we infer that these YSOs are the source of
ionizing photons. Both types of objects show evidence of shocks, with most of
the outflow sources showing a line of [S I] in the outflows and two of the red
sources showing the more highly excited [Ne III] and [S IV] lines in outflow
regions at some distance from the YSOs. The 4.5 micron emission seen in the
IRAC band 2 images of the outflow sources is not due to H2 lines, which are too
faint in the 5-10 micron wavelength region to be as strong as is needed to
account for the IRAC band 2 emission.Comment: 31 pages and 30 figures in the paper plus 11 figures from the online
Supporting Information. To be published in the MNRAS. Version 2 has many
small changes (typos, spelling, punctuation) and reordering of the Supporting
Information figures to make this version conform to the paper that will be
printed in MNRA
The active and passive populations of Extremely Red Objects
[abridged] The properties of galaxies with the reddest observed R-K colors
(Extremely Red Objects, EROs), including their apparent division into passive
and obscured active objects with roughly similar number densities, are a known
challenge for models of galaxy formation. We produce mock catalogues generated
by interfacing the predictions of the semi-analytical MORGANA model for the
evolution of galaxies in a Lambda-CDM cosmology with the spectro-photometric +
radiative transfer code GRASIL and Infrared (IR) template library to show that
the model correctly reproduces number counts, redshift distributions and active
fractions of R-K>5 sources. We test the robustness of our results against
different dust attenuations and, most importantly, against the inclusion of
TP-AGB stars in Simple Stellar Populations used to generate galaxy spectra, and
find that the inclusion of TP-AGBs has a relevant effect, in that it allows to
increase by a large factor the number of very red active objects at all color
cuts. We find that though the most passive and the most obscured active
galaxies have a higher probability of being selected as EROs, many EROs have
intermediate properties and the population does not show bimodality in specific
star formation rate (SSFR). We predict that deep observations in the Far-IR,
from 100 to 500 micron, are the most efficient way to constrain the SSFR of
these objects; we give predictions for future Herschel observations. Finally,
we test whether a simple evolutionary sequence for the formation of z=0 massive
galaxies, going through a sub-mm-bright phase and then a ERO phase, are typical
in this galaxy formation model. We find that this sequence holds for ~25 per
cent of z=0 massive galaxies, while the model typically shows a more complex
connection between sub-mm, ERO and massive galaxies. [abridged]Comment: 14 pages, 12 figures, MNRAS in pres
Using photo-elicitation to explore the lived experience of informal caregivers of individuals living with dementia
Objectives
This study aims to explore the subjective lived experience of informal caregivers supporting an individual with dementia.
Design
This study uses the interpretive phenomenological approach utilizing the method of photoâelicitation and inâdepth semiâstructured interviews.
Methods
Six individuals were given a disposable camera to capture photographs which they felt illustrated their own lived experiences of being a caregiver of an individual living with dementia. Photographs were printed and used to form discussion within an inâdepth semiâstructured interview. The photographs provided an innovative way of capturing the lived experiences of formal dementia caregivers and allowed the interview data to be grounded in their daily living, centring around their own lived experiences.
Results
Three themes emerged from data analysis: âconceptualising the role of informal caregiverâ, âsupport for the informal caregiverâ, and âthe caregivers own needsâ.
Conclusions
Findings demonstrated the complexity of the relationship between the caregiver and the person living with dementia, and the shift in this relationship specifically due to the role of carer, with notable differences between spousal caregivers and adultâchild caregivers. The importance of social, emotional, and practical support for caregivers was highlighted, as well as significance of the caregiver's individual needs
Mindfulness-based interventions in epilepsy: a systematic review
Mindfulness based interventions (MBIs) are increasingly used to help patients cope with physical and mental long-term conditions (LTCs). Epilepsy is associated with a range of mental and physical comorbidities that have a detrimental effect on quality of life (QOL), but it is not clear whether MBIs can help. We systematically reviewed the literature to determine the effectiveness of MBIs in people with epilepsy. Medline, Cochrane Central Register of Controlled Trials, EMBASE, CINAHL, Allied and Complimentary Medicine Database, and PsychInfo were searched in March 2016. These databases were searched using a combination of subject headings where available and keywords in the title and abstracts. We also searched the reference lists of related reviews. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Three randomised controlled trials (RCTs) with a total of 231 participants were included. The interventions were tested in the USA (nâ=â171) and China (Hong Kong) (nâ=â60). Significant improvements were reported in depression symptoms, quality of life, anxiety, and depression knowledge and skills. Two of the included studies were assessed as being at unclear/high risk of bias - with randomisation and allocation procedures, as well as adverse events and reasons for drop-outs poorly reported. There was no reporting on intervention costs/benefits or how they affected health service utilisation. This systematic review found limited evidence for the effectiveness of MBIs in epilepsy, however preliminary evidence suggests it may lead to some improvement in anxiety, depression and quality of life. Further trials with larger sample sizes, active control groups and longer follow-ups are needed before the evidence for MBIs in epilepsy can be conclusively determined
Photophysical and Photochemical Studies of Tricarbonyl Rhenium(I) N-Heterocyclic Carbene Complexes Containing Azide and Triazolate Ligands
Rhenium(I) N-heterocyclic carbene (NHC) complexes of the type fac-[Re(CO)3(NHC)L] with either azide or triazolate ancillary ligands L and pyridyl or pyrimidyl substituted imidazolyl units have been prepared and structurally characterised, and their photophysical and photochemical properties studied. All of the complexes exhibit phosphorescent emission from triplet metal-to-ligand (3MCLT) excited states, typical of tricarbonyl Re(I) complexes, with the triazolate bound complexes having higher quantum yields and longer decay lifetimes compared to the azide bound complexes. The complexes containing pyridyl substituted imidazolyl units are photoreactive when dissolved in acetonitrile and undergo photochemical CO dissociation, the rate of which is significantly greater in the azide cf. triazolate complex. The photochemical mechanism of the azide/pyridyl complex was analysed and appears to give the same products, albeit with different ratios, to previously reported complexes where L is a halide. A reaction mechanism is proposed
The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth
The short term variability of the Galactic cosmic ray flux (CRF) reaching
Earth has been previously associated with variations in the global low altitude
cloud cover. This CRF variability arises from changes in the solar wind
strength. However, cosmic ray variability also arises intrinsically from
variable activity of and motion through the Milky Way. Thus, if indeed the CRF
climate connection is real, the increased CRF witnessed while crossing the
spiral arms could be responsible for a larger global cloud cover and a reduced
temperature, thereby facilitating the occurrences of ice ages. This picture has
been recently shown to be supported by various data (Shaviv, 2001). In
particular, the variable CRF recorded in Iron meteorites appears to vary
synchronously with the appearance ice ages.
Here we expand upon the original treatment with a more thorough analysis and
more supporting evidence. In particular, we discuss the cosmic ray diffusion
model which considers the motion of the Galactic spiral arms. We also elaborate
on the structure and dynamics of the Milky Way's spiral arms. In particular, we
bring forth new argumentation using HI observations which imply that the
galactic spiral arm pattern speed appears to be that which fits the glaciation
period and the cosmic-ray flux record extracted from Iron meteorites. In
addition, we show that apparent peaks in the star formation rate history, as
deduced by several authors, coincides with particularly icy epochs, while the
long period of 1 to 2 Gyr before present, during which no glaciations are known
to have occurred, coincides with a significant paucity in the past star
formation rate.Comment: 33 pages, 11 figures. To Appear in New Astronom
Crimean-Congo Hemorrhagic Fever, Mauritania
A hospital outbreak of CCHF in Mauritania alerted authorities to sporadic cases occurring in the community; in all, 38 persons were infected
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