530 research outputs found
Detailed Chemical Abundances of Globular Clusters in Local Group Dwarf Galaxies
We present detailed chemical abundances of Fe, Ca and Ba for 17 globular
clusters (GCs) in 5 Local Group dwarf galaxies: NGC 205, NGC 6822, WLM, the SMC
and LMC. These abundances are part of a larger sample of over 20 individual
elements measured in GCs in these galaxies using a new analysis method for high
resolution, integrated light spectra. Our analysis also provides age and
stellar population constraints. The existence of GCs in dwarf galaxies with a
range of ages implies that there were episodes of rapid star formation
throughout the history of these galaxies; the abundance ratios of these
clusters suggest that the duration of these burst varied considerably from
galaxy to galaxy. We find evolution of Fe, Ca, and Ba with age in the LMC, SMC,
and NGC 6822 that is consistent with extended, lower-efficiency SF between
bursts, with an increasing contribution of low-metallicity AGB ejecta at late
times. Our sample of GCs in NGC 205 and WLM are predominantly old and
metal-poor with high [Ca/Fe] ratios, implying that the early history of these
galaxies was marked by consistently high SF rates.Comment: 2 pages, To appear in the proceedings of the conference "A Universe
of Dwarf Galaxies" (Lyon, June 14-18, 2010
Analytic continuation of residue currents
Let be a complex manifold and f\colon X\to \C^p a holomorphic mapping
defining a complete intersection. We prove that the iterated Mellin transform
of the residue integral associated to has an analytic continuation to a
neighborhood of the origin in \C^p
Global profiling of the proteomic changes associated with the post-testicular maturation of mouse spermatozoa
Spermatozoa acquire fertilization potential during passage through a highly specialized region of the extratesticular ductal system known as the epididymis. In the absence of de novo gene transcription or protein translation, this functional transformation is extrinsically driven via the exchange of varied macromolecular cargo between spermatozoa and the surrounding luminal plasma. Key among these changes is a substantive remodeling of the sperm proteomic architecture, the scale of which has yet to be fully resolved. Here, we have exploited quantitative mass spectrometry-based proteomics to define the extent of changes associated with the maturation of mouse spermatozoa; reporting the identity of >6,000 proteins, encompassing the selective loss and gain of several hundred proteins. Further, we demonstrate epididymal-driven activation of RHOAmediated signaling pathways is an important component of sperm maturation. These data contribute molecular insights into the complexity of proteomic changes associated with epididymal sperm maturation.David A. Skerrett-Byrne, Amanda L. Anderson, Elizabeth G. Bromfield, Ilana R. Bernstein, Jess E. Mulhall, John E. Schjenken, Matthew D. Dun, Sean J. Humphrey, and Brett Nixo
Immortalized mouse caput epididymal epithelial (mECap18) cell line recapitulates the in-vivo environment
OnlinePublResiding between the testes and the vas deferens, the epididymis is a highly convoluted tubule whose unique luminal microenvironment is crucial for the functional maturation of spermatozoa. This microenvironment is created by the combined secretory and resorptive activity of the lining epididymal epithelium, including the release of extracellular vesicles (epididymosomes), which encapsulate fertility modulating proteins and a myriad of small non-coding RNAs (sncRNAs) that are destined for delivery to recipient sperm cells. To enable investigation of this intercellular communication nexus, we have previously developed an immortalized mouse caput epididymal epithelial cell line (mECap18). Here, we describe the application of label-free mass spectrometry to characterize the mECap18 cell proteome and compare this to the proteome of native mouse caput epididymal epithelial cells. We report the identification of 5,313 mECap18 proteins, as many as 75.8% of which were also identified in caput epithelial cells wherein they mapped to broadly similar protein classification groupings. Furthermore, key pathways associated with protein synthesis (e.g., EIF2 signaling) and cellular protection in the male reproductive tract (e.g., sirtuin signaling) were enriched in both proteomes. This comparison supports the utility of the mECap18 cell line as a tractable in-vitro model for studying caput epididymal epithelial cell function.Jess E. Mulhall, Natalie A. Trigg, Ilana R. Bernstein, Amanda L. Anderson, Heather C. Murray, Petra Sipilä, Tessa Lord, John E. Schjenken, Brett Nixon, David A. Skerrett-Byrn
Statistical Theory for Incoherent Light Propagation in Nonlinear Media
A novel statistical approach based on the Wigner transform is proposed for
the description of partially incoherent optical wave dynamics in nonlinear
media. An evolution equation for the Wigner transform is derived from a
nonlinear Schrodinger equation with arbitrary nonlinearity. It is shown that
random phase fluctuations of an incoherent plane wave lead to a Landau-like
damping effect, which can stabilize the modulational instability. In the limit
of the geometrical optics approximation, incoherent, localized, and stationary
wave-fields are shown to exist for a wide class of nonlinear media.Comment: 4 pages, REVTeX4. Submitted to Physical Review E. Revised manuscrip
On Kedlaya type inequalities for weighted means
In 2016 we proved that for every symmetric, repetition invariant and Jensen
concave mean the Kedlaya-type inequality holds for an
arbitrary ( stands for the arithmetic mean). We are going
to prove the weighted counterpart of this inequality. More precisely, if
is a vector with corresponding (non-normalized) weights
and denotes the weighted mean then, under
analogous conditions on , the inequality holds for every and such that the sequence
is decreasing.Comment: J. Inequal. Appl. (2018
Evaluation of a visual aid toolkit for water, sanitation, and hygiene education in the Bateyes of La Romana, Dominican Republic
Astrophysical Axion Bounds
Axion emission by hot and dense plasmas is a new energy-loss channel for
stars. Observational consequences include a modification of the solar
sound-speed profile, an increase of the solar neutrino flux, a reduction of the
helium-burning lifetime of globular-cluster stars, accelerated white-dwarf
cooling, and a reduction of the supernova SN 1987A neutrino burst duration. We
review and update these arguments and summarize the resulting axion
constraints.Comment: Contribution to Axion volume of Lecture Notes in Physics, 20 pages, 3
figure
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
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