944 research outputs found
Optimal Moments for the Analysis of Peculiar Velocity Surveys II: Testing
Analyses of peculiar velocity surveys face several challenges, including low
signal--to--noise in individual velocity measurements and the presence of
small--scale, nonlinear flows. This is the second in a series of papers in
which we describe a new method of overcoming these problems by using data
compression as a filter with which to separate large--scale, linear flows from
small--scale noise that can bias results. We demonstrate the effectiveness of
our method using realistic catalogs of galaxy velocities drawn from N--body
simulations. Our tests show that a likelihood analysis of simulated catalogs
that uses all of the information contained in the peculiar velocities results
in a bias in the estimation of the power spectrum shape parameter and
amplitude , and that our method of analysis effectively removes this
bias. We expect that this new method will cause peculiar velocity surveys to
re--emerge as a useful tool to determine cosmological parameters.Comment: 28 pages, 9 figure
Optimal Moments for the Analysis of Peculiar Velocity Surveys
We present a new method for the analysis of peculiar velocity surveys which
removes contributions to velocities from small scale, nonlinear velocity modes
while retaining information about large scale motions. Our method utilizes
Karhunen--Lo\`eve methods of data compression to construct a set of moments out
of the velocities which are minimally sensitive to small scale power. The set
of moments are then used in a likelihood analysis. We develop criteria for the
selection of moments, as well as a statistic to quantify the overall
sensitivity of a set of moments to small scale power. Although we discuss our
method in the context of peculiar velocity surveys, it may also prove useful in
other situations where data filtering is required.Comment: 25 Pages, 3 figures. Submitted to Ap
CARRYING A BALL CAN INFLUENCE SIDESTEPPING MECHANICS IN RUGBY
Sidestepping mechanics have been implicated as a risk factor for knee injury in rugby. Carrying a ball is proposed to alter movement patterns. Therefore the purpose of the study was to examine the effects of sidestepping with a ball compared to sidestepping without a ball on lower-extremity biomechanics in male rugby athletes. Three-dimensional kinematics of 18 male rugby athletes were recorded during a maximal effort 45° sidestepping task without and with a ball. Sidestepping with a ball resulted in 15% greater knee adduction angle during weight acceptance and 18% greater hip adduction angle during peak pushoff than without a ball. Future biomechanical evaluations of athletes require the inclusion of the ball specific to the sport to ensure accurate interpretation of movement patterns
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Improvement of the Immunoisolation Capacity of PEG Hydrogels through Bioactive Modifications
Cell-based therapies are a promising approach for the treatment of diseases such as Type I diabetes mellitus (TIDM), where endogenous insulin production is restored via delivery of insulin-producing beta-cells or islet of Langerhans clusters. Tissue rejection by the host\u27s immune system, however, is a major hurdle limiting the broad use of transplanted tissues, so beta-cell-based therapies require systemic immunosuppression. To reduce this requirement, tissues have been encapsulated within natural and synthetic barrier materials in a process known as immunoisolation. Immunoisolation materials, including poly (ethylene glycol) (PEG) hydrogels, create physical barriers between host immune cells and donor tissue while enabling the diffusion of small molecules like nutrients and oxygen. Unmodified immunoisolation barriers, however, are unable to prevent the diffusion of small cytotoxic molecules, including reactive oxygen species (ROS) (e.g., superoxide) and cytokines. This research investigated strategies to introduce immunoactive modifications to PEG hydrogels for the purpose of improving their immunoisolation capacity. Towards this, a polymerizable superoxide dismutase mimetic (SODm) was covalently tethered within beta-cell-laden hydrogels to significantly increase cell survival following challenges with superoxide, a major inflammatory mediator of the immune response. Next, photoiniferter chemistry was employed to polymerize PEG chains co-functionalized with an apoptosis inducing factor (anti-fas) and a T cell adhesion ligand (ICAM-1) to locally reduce, through apoptosis, the population of T cells, the adaptive immune responder cells implicated in islet transplant rejection. Further, conformal, immunoactive coatings were formed directly on the surfaces of cell-laden PEG hydrogels using a versatile, reactive dip-coating strategy to present a high density of immunoactive signal while maintaining encapsulated cell cytocompatibility. Finally, towards preventing the development of deleterious adaptive immunity altogether, immunosuppressive hydrogels modified with TGF-beta1 and IL-10 were introduced, and their capacity to reduce dendritic cell maturation was highlighted. The immunoactive materials developed within this thesis suggest innovative strategies for the engineering of future immunoisolation barriers to provide localized and targeted protection of transplanted cells
Immunohistochemical study of morphology and distribution of CD163+ve macrophages in the normal adult equine gastrointestinal tract
Intestinal macrophages are the largest group of mononuclear phagocytes in the body and play a role in intestinal innate immunity, neuroimmune interactions and maintaining intestinal homeostasis. Conversely, they also are implicated in numerous pathologies of the gastrointestinal tract, such as postoperative ileus and inflammatory bowel disease. As a result, macrophages could be potential therapeutic targets. To date, there are limited studies on the morphology and distribution of macrophages in the equine gastrointestinal tract (GIT). The aim of this study was to identify the location and abundance of resident macrophages in the equine GIT using CD163 as an immunohistochemical marker. Tissue samples were obtained post-mortem from 14 sites along the gastrointestinal tracts of 10 horses free from gastrointestinal disease; sample sites extended from the stomach to the small colon. CD163 cells were present in all regions of the equine GIT from stomach to small colon. CD163 cells were also identified in all tissue layers of the intestinal wall, namely, mucosa, submucosa, muscularis externa (ME), myenteric plexus and serosa. Consistent with a proposed function in regulation of intestinal motility, CD163 cells were regularly distributed within the ME, with accumulations closely associated with the myenteric plexus and effector cells such as neurons and the interstitial cells of Cajal (ICC)
ATXR5 and ATXR6 are H3K27 monomethyltransferases required for chromatin structure and gene silencing.
Constitutive heterochromatin in Arabidopsis thaliana is marked by repressive chromatin modifications, including DNA methylation, histone H3 dimethylation at Lys9 (H3K9me2) and monomethylation at Lys27 (H3K27me1). The enzymes catalyzing DNA methylation and H3K9me2 have been identified; alterations in these proteins lead to reactivation of silenced heterochromatic elements. The enzymes responsible for heterochromatic H3K27me1, in contrast, remain unknown. Here we show that the divergent SET-domain proteins ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) and ATXR6 have H3K27 monomethyltransferase activity, and atxr5 atxr6 double mutants have reduced H3K27me1 in vivo and show partial heterochromatin decondensation. Mutations in atxr5 and atxr6 also lead to transcriptional activation of repressed heterochromatic elements. Notably, H3K9me2 and DNA methylation are unaffected in double mutants. These results indicate that ATXR5 and ATXR6 form a new class of H3K27 methyltransferases and that H3K27me1 represents a previously uncharacterized pathway required for transcriptional repression in Arabidopsis
Stochastic model of transcription factor-regulated gene expression
We consider a stochastic model of transcription factor (TF)-regulated gene
expression. The model describes two genes: Gene A and Gene B which synthesize
the TFs and the target gene proteins respectively. We show through analytic
calculations that the TF fluctuations have a significant effect on the
distribution of the target gene protein levels when the mean TF level falls in
the highest sensitive region of the dose-response curve. We further study the
effect of reducing the copy number of Gene A from two to one. The enhanced TF
fluctuations yield results different from those in the deterministic case. The
probability that the target gene protein level exceeds a threshold value is
calculated with a knowledge of the probability density functions associated
with the TF and target gene protein levels. Numerical simulation results for a
more detailed stochastic model are shown to be in agreement with those obtained
through analytic calculations. The relevance of these results in the context of
the genetic disorder haploinsufficiency is pointed out. Some experimental
observations on the haploinsufficiency of the tumour suppressor gene, Nkx3.1,
are explained with the help of the stochastic model of TF-regulated gene
expression.Comment: 17 pages, 11 figures. Accepted for publication in Physical Biolog
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