1,033 research outputs found
Asymptotic growth and least common multiples in groups
In this article we relate word and subgroup growth to certain functions that
arise in the quantification of residual finiteness. One consequence of this
endeavor is a pair of results that equate the nilpotency of a finitely
generated group with the asymptotic behavior of these functions. The second
half of this article investigates the asymptotic behavior of two of these
functions. Our main result in this arena resolves a question of Bogopolski from
the Kourovka notebook concerning lower bounds of one of these functions for
nonabelian free groups.Comment: 13 page
Bertrand's postulate and subgroup growth
In this article we investigate the L^1-norm of certain functions on groups
called divisibility functions. Using these functions, their connection to
residual finiteness, and integration theory on profinite groups, we define the
residual average of a finitely generated group. One of the main results in this
article is the finiteness of residual averages on finitely generated linear
groups. Whether or not the residual average is finite depends on growth rates
of indices of finite index subgroups. Our results on index growth rates are
analogous to results on gaps between primes, and provide a variant of the
subgroup growth function, which may be of independent interest.Comment: 33 page
Inverse Cascade Evidenced by Information Entropy of Passive Scalars in Submerged Canopy Flows
Turbulent mixing of scalars within canopies is investigated using a flume experiment with canopy-like rods of height h mounted to the channel bed. The data comprised a time sequence of high-resolution images of a dye recorded in a plane parallel to the bed at z/h= 0.2. Image processing shows that von KĆ”rmĆ”n wakes shed by canopy drag and downward turbulent transport from upper canopy layers impose distinct scaling regimes on the scalar spectrum. Measures from information theory are then used to explore the dominant directionality of the interaction between small and large scales underlying these two spectral regimes, showing that the arrival of sweeps from aloft establishes an inertial-range spectrum with forward āinformationā cascade. In contrast, wake growth with downstream distance leads to persistent upscale transfer (inverse cascade) of scalar variance, which hints at their nondiffusive character and the significance of the stem diameter as an active length scale in canopy turbulence
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The Functionality of the three-sited Ferroxidase center of E. coli Bacterial Ferritin (EcFtnA)
At least three ferritins are found in the bacterium Escherichia coli, the heme-containing bacterioferritin
(EcBFR) and two non-heme bacterial ferritins (EcFtnA and EcFtnB). In addition to the conserved A- and
B-sites of the diiron ferroxidase center, EcFtnA has a third iron-binding site (the C-site) of unknown
function that is nearby the diiron site. In the present work, the complex chemistry of iron oxidation and
deposition in EcFtnA has been further defined through a combination of oximetry, pH stat, stopped-flow
and conventional kinetics, UV-visible, fluorescence and EPR spectroscopic measurements on the wildtype
protein and site-directed variants of the A-, B- and C-sites. The data reveal that, while H2O2 is a
product of dioxygen reduction in EcFtnA and oxidation occurs with a stoichiometry of Fe(II)/O2 ~ 3:1,
most of the H2O2 produced is consumed in subsequent reactions with a 2:1 Fe(II)/H2O2 stoichiometry,
thus suppressing hydroxyl radical formation. While the A- and B-sites are essential for rapid iron
oxidation, the C-site slows oxidation and suppresses iron turnover at the ferroxidase center. A tyrosyl
radical, assigned to Tyr24 near the ferroxidase center, is formed during iron oxidation and its possible
significance to the function of the protein is discussed. Taken as a whole, the data indicate that there are
multiple iron-oxidation pathways in EcFtnA with O2 and H2O2 as oxidants. Furthermore, the data are
inconsistent with the C-site being a transit site, providing iron to the A- and B-sites, and does not support a
universal mechanism for iron oxidation in all ferritins as recently proposed
Residual Finiteness Growths of Virtually Special Groups
Let be a virtually special group. Then the residual finiteness growth of
is at most linear. This result cannot be found by embedding into a
special linear group. Indeed, the special linear group
, for , has residual finiteness growth
.Comment: Updated version contains minor changes incorporating referee
comments/suggestions and a simplified proof of Lemma 4.
Stationary distributions for diffusions with inert drift
Consider reflecting Brownian motion in a bounded domain in that acquires drift in proportion to the amount of local time spent on the boundary of the domain. We show that the stationary distribution for the joint law of the position of the reflecting Brownian motion and the value of the drift vector has a product form. Moreover, the first component is uniformly distributed on the domain, and the second component has a Gaussian distribution. We also consider more general reflecting diffusions with inert drift as well as processes where the drift is given in terms of the gradient of a potential
Data on CUX1 isoforms in idiopathic pulmonary fibrosis lung and systemic sclerosis skin tissue sections
This data article contains complementary figures related to the
research article entitled, āTransforming growth factor-Ī²-induced
CUX1 isoforms are associated with fibrosis in systemic sclerosis
lung fibroblastsā (Ikeda et al. (2016) [2], http://dx.doi.org/10.1016/j.
bbrep.2016.06.022), which presents that TGF-Ī² increased CUX1
binding in the proximal promoter and enhancer of the COL1A2 and
regulated COL1. Further, in the scleroderma (SSc) lung and diffuse
alveolar damage lung sections, CUX1 localized within the Ī±-
smooth muscle actin (Ī±-SMA) positive cells (Fragiadaki et al., 2011)
[1], āHigh doses of TGF-beta potently suppress type I collagen via
the transcription factor CUX1ā (Ikeda et al., 2016) [2]. Here we
show that CUX1 isoforms are localized within Ī±-smooth muscle
actin-positive cells in SSc skin and idiopathic pulmonary fibrosis
(IPF) lung tissue sections. In particular, at the granular and prickle
cell layers in the SSc skin sections, CUX1 and Ī±-SMA are colocalized.
In addition, at the fibrotic loci in the IPF lung tissue
sections, CUX1 localized within the Ī±-smooth muscle actin (Ī±-
SMA) positive cells
Vortex Collisions: Crossing or Recombination?
We investigate the collision of two vortex lines moving with viscous dynamics
and driven towards each other by an applied current. Using London theory in the
approach phase we observe a non-trivial vortex conformation producing
anti-parallel segments; their attractive interaction triggers a violent
collision. The collision region is analyzed using the time-dependent
Ginzburg-Landau equation. While we find vortices will always recombine through
exchange of segments, a crossing channel appears naturally through a double
collision process.Comment: 4 pages, 3 figure
Omega-3 canola oil effectively replaces fish oil as a new safe dietary source of docosahexaenoic acid (DHA) in feed for juvenile Atlantic salmon
Limited availability of fish oils (FO), rich in n-3 long-chain (ā„C20) PUFA, is a major constraint for further growth of the aquaculture industry. Long-chain n-3 rich oils from crops GM with algal genes are promising new sources for the industry. This project studied the use of a newly developed n-3 canola oil (DHA-CA) in diets of Atlantic salmon fingerlings in freshwater. The DHA-CA oil has high proportions of the n-3 fatty acids (FA) 18 : 3n-3 and DHA and lower proportions of n-6 FA than conventional plant oils. Levels of phytosterols, vitamin E and minerals in the DHA-CA were within the natural variation of commercial canola oils. Pesticides, mycotoxins, polyaromatic hydrocarbons and heavy metals were below lowest qualifiable concentration. Two feeding trials were conducted to evaluate effects of two dietary levels of DHA-CA compared with two dietary levels of FO at two water temperatures. Fish increased their weight approximately 20-fold at 16Ā°C and 12-fold at 12Ā°C during the experimental periods, with equal growth in salmon fed the FO diets compared with DHA-CA diets. Salmon fed DHA-CA diets had approximately the same EPA+DHA content in whole body as salmon fed FO diets. Gene expression, lipid composition and oxidative stress-related enzyme activities showed only minor differences between the dietary groups, and the effects were mostly a result of dietary oil level, rather than the oil source. The results demonstrated that DHA-CA is a safe and effective replacement for FO in diets of Atlantic salmon during the sensitive fingerling life-stage.acceptedVersio
Challenges and opportunities in transdisciplinary science: The experience of next generation scientists in an agriculture and climate research collaboration
Agriculture in the twenty-first century faces unprecedented challenges from increasing climate variability to growing demands on natural resources to globalizing economic markets. These emerging agricultural issues, spanning both human and natural dimensions, are uniquely formulated, exceedingly complex, and difficult to address within existing disciplinary domains (Eigenbrode et al. 2007; Reganold et al. 2011; Foley et al. 2005; Hansen et al. 2013). Therefore, the next generation of scientists working on these issues must not only be highly trained within a disciplinary context but must also have the capacity to collaborate with others to solve systems-level problems
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