3,420 research outputs found
Landscape of standing variation for tandem duplications in Drosophila yakuba and Drosophila simulans
We have used whole genome paired-end Illumina sequence data to identify
tandem duplications in 20 isofemale lines of D. yakuba, and 20 isofemale lines
of D. simulans and performed genome wide validation with PacBio long molecule
sequencing. We identify 1,415 tandem duplications that are segregating in D.
yakuba as well as 975 duplications in D. simulans, indicating greater variation
in D. yakuba. Additionally, we observe high rates of secondary deletions at
duplicated sites, with 8% of duplicated sites in D. simulans and 17% of sites
in D. yakuba modified with deletions. These secondary deletions are consistent
with the action of the large loop mismatch repair system acting to remove
polymorphic tandem duplication, resulting in rapid dynamics of gain and loss in
duplicated alleles and a richer substrate of genetic novelty than has been
previously reported. Most duplications are present in only single strains,
suggesting deleterious impacts are common. D. simulans shows larger numbers of
whole gene duplications in comparison to larger proportions of gene fragments
in D. yakuba. D. simulans displays an excess of high frequency variants on the
X chromosome, consistent with adaptive evolution through duplications on the D.
simulans X or demographic forces driving duplicates to high frequency. We
identify 78 chimeric genes in D. yakuba and 38 chimeric genes in D. simulans,
as well as 143 cases of recruited non-coding sequence in D. yakuba and 96 in D.
simulans, in agreement with rates of chimeric gene origination in D.
melanogaster. Together, these results suggest that tandem duplications often
result in complex variation beyond whole gene duplications that offers a rich
substrate of standing variation that is likely to contribute both to
detrimental phenotypes and disease, as well as to adaptive evolutionary change.Comment: Revised Version- Accepted at Molecular Biology and Evolutio
Photon statistics from coupled quantum dots
We present an optical study of closely-spaced self-assembled InAs/GaAs
quantum dots. The energy spectrum and correlations between photons subsequently
emitted from a single pair provide not only clear evidence of coupling between
the quantum dots but also insight into the coupling mechanism. Our results are
in agreement with recent theories predicting that tunneling is largely
suppressed between nonidentical quantum dots and that the interaction is
instead dominated by dipole-dipole coupling and phonon-assisted energy transfer
processes.Comment: 4 pages, 4 figures, to appear in Phys. Re
Frequency control of photonic crystal membrane resonators by mono-layer deposition
We study the response of GaAs photonic crystal membrane resonators to thin
film deposition. Slow spectral shifts of the cavity mode of several nanometers
are observed at low temperatures, caused by cryo-gettering of background
molecules. Heating the membrane resets the drift and shielding will prevent
drift altogether. In order to explore the drift as a tool to detect surface
layers, or to intentionally shift the cavity resonance frequency, we studied
the effect of self-assembled monolayers of polypeptide molecules attached to
the membranes. The 2 nm thick monolayers lead to a discrete step in the
resonance frequency and partially passivate the surface.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let
Mouse Rad1 deletion enhances susceptibility for skin tumor development
Cells are constantly exposed to stresses from cellular metabolites as well as environmental genotoxins. DNA damage caused by these genotoxins can be efficiently fixed by DNA repair in cooperation with cell cycle checkpoints. Unrepaired DNA lesions can lead to cell death, gene mutation and cancer. The Rad1 protein, evolutionarily conserved from yeast to humans, exists in cells as monomer as well as a component in the 9-1-1 protein complex. Rad1 plays crucial roles in DNA repair and cell cycle checkpoint control, but its contribution to carcinogenesis is unknown.
To address this question, we constructed mice with a deletion of Mrad1. Matings between heterozygous Mrad1 mutant mice produced Mrad1+/+ and Mrad1+/- but no Mrad1-/- progeny, suggesting the Mrad1 null is embryonic lethal. Mrad1+/- mice demonstrated no overt abnormalities up to one and half years of age. DMBA-TPA combinational treatment was used to induce tumors on mouse skin. Tumors were larger, more numerous, and appeared earlier on the skin of Mrad1+/- mice compared to Mrad1+/+ animals. Keratinocytes isolated from Mrad1+/- mice had significantly more spontaneous DNA double strand breaks, proliferated slower and had slightly enhanced spontaneous apoptosis than Mrad1+/+ control cells.
These data suggest that Mrad1 is important for preventing tumor development, probably through maintaining genomic integrity. The effects of heterozygous deletion of Mrad1 on proliferation and apoptosis of keratinocytes is different from those resulted from Mrad9 heterozygous deletion (from our previous study), suggesting that Mrad1 also functions independent of Mrad9 besides its role in the Mrad9-Mrad1-Mhus1 complex in mouse cells
O-Band Subwavelength Grating Filters in a Monolithic Photonics Technology
The data communications industry has begun transitioning from electrical to
optical interconnects in datacenters in order to overcome performance
bottlenecks and meet consumer needs. To mitigate the costs associated with this
change and achieve performance for 5G and beyond, it is crucial to explore
advanced photonic devices that can enable high-bandwidth interconnects via
wavelength-division multiplexing (WDM) in photonic integrated circuits.
Subwavelength grating (SWG) filters have shown great promise for WDM
applications. However, the small feature sizes necessary to implement these
structures have prohibited them from penetrating into industrial applications.
To explore the manufacturability and performance of SWG filters in an
industrial setting, we fabricate and characterize O-band subwavelength grating
filters using the monolithic photonics technology at GLOBALFOUNDRIES (GF). We
demonstrate a low drop channel loss of -1.2 dB with a flat-top response, a high
extinction ratio of -30 dB, a 3 dB channel width of 5 nm and single-source
thermal tunability without shape distortion. This filter structure was designed
using elements from the product design kit provided by GF and functions in a
compact footprint of 0.002 mm2 with a minimum feature size of 150 nm.Comment: 4 pages, 3 figure
Diagnosing and predicting wind turbine faults from SCADA data using support vector machines
Unscheduled or reactive maintenance on wind turbines due to component failure incurs significant downtime and, in turn, loss of revenue. To this end, it is important to be able to perform maintenance before it's needed. To date, a strong effort has been applied to developing Condition Monitoring Systems (CMSs) which rely on retrofitting expensive vibration or oil analysis sensors to the turbine. Instead, by performing complex analysis of existing data from the turbine's Supervisory Control and Data Acquisition (SCADA) system, valuable insights into turbine performance can be obtained at a much lower cost. In this paper, fault and alarm data from a turbine on the Southern coast of Ireland is analysed to identify periods of nominal and faulty operation. Classification techniques are then applied to detect and diagnose faults by taking into account other SCADA data such as temperature, pitch and rotor data. This is then extended to allow prediction and diagnosis in advance of specific faults. Results are provided which show recall scores generally above 80\% for fault detection and diagnosis, and prediction up to 24 hours in advance of specific faults, representing significant improvement over previous techniques
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