831 research outputs found
EFFECT OF ANKLE STABILIZERS ON SIDE SHUFFLE PERFORMANCE
The purpose of this study was to examine the effect of ankle stabilizers on side shuffle performance. Eight healthy and active college students randomly performed six side shuffle trials in both directions; three without and three with an ankle stabilizer. Two dimensional (2D) kinematic and kinetic data were collected. The only significant difference was found in ankle ROM during braking and propulsive phases while traveling in both directions. All the kinetic data (impulses and peak forces in vertical and horizontal directions) were similar between conditions during braking and propulsive phases. Although the average horizontal velocity was slightly lower in the ankle stabilizer condition, the statistical significance was not met (P=0.06). The results suggested that semi-rigid ankle stabilizer had no significant effect on the side shuffle performance
Glycan Engineering for Cell and Developmental Biology
Cell-surface glycans are a diverse class of macromolecules that participate in many key biological processes, including cell-cell communication, development, and disease progression. Thus, the ability to modulate the structures of glycans on cell surfaces provides a powerful means not only to understand fundamental processes but also to direct activity and elicit desired cellular responses. Here, we describe methods to sculpt glycans on cell surfaces and highlight recent successes in which artificially engineered glycans have been employed to control biological outcomes such as the immune response and stem cell fate
To Score or Not to Score? Estimates of a Sponsored Search Auction Model
We estimate a structural model of a sponsored search auction model. To accomodate the "position paradox", we relax the assumption of decreasing click volumes with position ranks, which is often assumed in the literature. Using data from "Website X", one of the largest online market places in China, we find that merchants of different qualities adopt different bidding strategies: high quality merchants bid more aggressively for informative keywords, while low quality merchants are more likely to be sorted to the top positions for value keywords. Counterfactual evaluations show that the price trend becomes steeper after moving to a score-weighted generalized second price auction, with much higher prices obtained for the top position but lower prices for the other positions. Overall, there is only a very modest change in total revenue from introducing popularity scoring, despite the intent in bid scoring to reward popular merchants with price discounts
Synthetic probes of glycosaminoglycan function
Glycosaminoglycans (GAGs) participate in many critical biological processes by modulating the activities of a wide range of proteins, including growth factors, chemokines, and viral receptors. Recent studies using synthetic oligosaccharides and glycomimetic polymers have established the importance of specific structural determinants in controlling GAG function. These findings illustrate the power of synthetic molecules to elucidate glycan-mediated signaling events, as well as the prospect of further advancements to understand the roles of GAGs in vivo and explore their therapeutic potential
Sirolimus Associated Pneumonitis after Nonmyeloablative Peripheral Blood Stem Cell Transplant for Sickle Cell Disease
Methods for the Detection, Study, and Dynamic Profiling of O-GlcNAc Glycosylation
The addition of O-linked β-N-acetylglucosamine (O-GlcNAc) to serine/threonine residues of proteins is a ubiquitous posttranslational modification found in all multicellular organisms. Like phosphorylation, O-GlcNAc glycosylation (O-GlcNAcylation) is inducible and regulates a myriad of physiological and pathological processes. However, understanding the diverse functions of O-GlcNAcylation is often challenging due to the difficulty of detecting and quantifying the modification. Thus, robust methods to study O-GlcNAcylation are essential to elucidate its key roles in the regulation of individual proteins, complex cellular processes, and disease. In this chapter, we describe a set of chemoenzymatic labeling methods to (1) detect O-GlcNAcylation on proteins of interest, (2) monitor changes in both the total levels of O-GlcNAcylation and its stoichiometry on proteins of interest, and (3) enable mapping of O-GlcNAc to specific serine/threonine residues within proteins to facilitate functional studies. First, we outline a procedure for the expression and purification of a multiuse mutant galactosyltransferase enzyme (Y289L GalT). We then describe the use of Y289L GalT to modify O-GlcNAc residues with a functional handle, N-azidoacetylgalactosamine (GalNAz). Finally, we discuss several applications of the copper-catalyzed azide-alkyne cycloaddition “click” reaction to attach various alkyne-containing chemical probes to GalNAz and demonstrate how this functionalization of O-GlcNAc-modified proteins can be used to realize (1)–(3) above. Overall, these methods, which utilize commercially available reagents and standard protein analytical tools, will serve to advance our understanding of the diverse and important functions of O-GlcNAcylation
Observational and Dynamical Characterization of Main-Belt Comet P/2010 R2 (La Sagra)
We present observations of comet-like main-belt object P/2010 R2 (La Sagra)
obtained by Pan-STARRS 1 and the Faulkes Telescope-North on Haleakala in
Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on
Mauna Kea, the Danish 1.54 m telescope at La Silla, and the Isaac Newton
Telescope on La Palma. An antisolar dust tail is observed from August 2010
through February 2011, while a dust trail aligned with the object's orbit plane
is also observed from December 2010 through August 2011. Assuming typical phase
darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag
between August 2010 and December 2010, suggesting that dust production is
ongoing over this period. These results strongly suggest that the observed
activity is cometary in nature (i.e., driven by the sublimation of volatile
material), and that P/La Sagra is therefore the most recent main-belt comet to
be discovered. We find an approximate absolute magnitude for the nucleus of
H_R=17.9+/-0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an
albedo of p=0.05. Using optical spectroscopy, we find no evidence of
sublimation products (i.e., gas emission), finding an upper limit CN production
rate of Q_CN<6x10^23 mol/s, from which we infer an H2O production rate of
Q_H2O<10^26 mol/s. Numerical simulations indicate that P/La Sagra is
dynamically stable for >100 Myr, suggesting that it is likely native to its
current location and that its composition is likely representative of other
objects in the same region of the main belt, though the relatively close
proximity of the 13:6 mean-motion resonance with Jupiter and the (3,-2,-1)
three-body mean-motion resonance with Jupiter and Saturn mean that dynamical
instability on larger timescales cannot be ruled out.Comment: 23 pages, 13 figures, accepted for publication in A
The 2016 Reactivations of Main-Belt Comets 238P/Read and 288P/(300163) 2006 VW139
We report observations of the reactivations of main-belt comets 238P/Read and
288P/(300163) 2006 VW139, that also track the evolution of each object's
activity over several months in 2016 and 2017. We additionally identify and
analyze archival SDSS data showing 288P to be active in 2000, meaning that both
238P and 288P have now each been confirmed to be active near perihelion on
three separate occasions. From data obtained of 288P from 2012-2015 when it
appeared inactive, we find best-fit R-band H,G phase function parameters of
H_R=16.80+/-0.12 mag and G_R=0.18+/-0.11, corresponding to effective component
radii of r_c=0.80+/-0.04 km, assuming a binary system with equally-sized
components. Fitting linear functions to ejected dust masses inferred for 238P
and 288P soon after their observed reactivations in 2016, we find an initial
average net dust production rate of 0.7+/-0.3 kg/s and a best-fit start date of
2016 March 11 (when the object was at a true anomaly of -63 deg) for 238P, and
an initial average net dust production rate of 5.6+/-0.7 kg/s and a best-fit
start date of 2016 August 5 (when the object was at a true anomaly of -27 deg)
for 288P. Applying similar analyses to archival data, we find similar start
points for previous active episodes for both objects, suggesting that minimal
mantle growth or ice recession occurred between the active episodes in
question. Some changes in dust production rates between active episodes are
detected, however. More detailed dust modeling is suggested to further clarify
the process of activity evolution in main-belt comets.Comment: 21 pages, 9 figures, accepted by A
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