87 research outputs found
A Role for Actin, Cdc1p, and Myo2p in the Inheritance of Late Golgi Elements in \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e
In Saccharomyces cerevisiae, Golgi elements are present in the bud very early in the cell cycle. We have analyzed this Golgi inheritance process using fluorescence microscopy and genetics. In rapidly growing cells, late Golgi elements show an actin-dependent concentration at sites of polarized growth. Late Golgi elements are apparently transported into the bud along actin cables and are also retained in the bud by a mechanism that may involve actin. A visual screen for mutants defective in the inheritance of late Golgi elements yielded multiple alleles of CDC1. Mutations in CDC1 severely depolarize the actin cytoskeleton, and these mutations prevent late Golgi elements from being retained in the bud. The efficient localization of late Golgi elements to the bud requires the type V myosin Myo2p, further suggesting that actin plays a role in Golgi inheritance. Surprisingly, early and late Golgi elements are inherited by different pathways, with early Golgi elements localizing to the bud in a Cdc1p- and Myo2p-independent manner. We propose that early Golgi elements arise from ER membranes that are present in the bud. These two pathways of Golgi inheritance in S. cerevisiae resemble Golgi inheritance pathways in vertebrate cells
Osseous changes following reverse total shoulder arthroplasty combined with latissimus dorsi transfer: a case series
Background: This is the first report on the incidence of proximal humerus osseous changes and associated clinical consequences in reverse total shoulder arthroplasty combined with a latissimus dorsi tendon transfer (RTSA+LDT).
Methods: A multicenter, retrospective review identified all patients who had undergone a primary RTSA+LDT and had at least 3-month radiographic follow-up between 2012 and 2017. Data collection included demographics, oral steroid use, repair technique for LDT fixation, radiographic humeral osseous changes, complications, and need for revision surgery.
Results: Twenty-four patients were included with an average age of 70.7 ± 7.9 years and follow-up of 16.3 (3-50) months. Ten patients (41.7%) developed osseous changes at the transfer location. There was no increased risk of developing osseous changes based on the surgical fixation technique (P = .421). Average time to earliest radiographic detection of osseous changes was 2.7 ± 1.7 months, with all changes occurring at or before 6 months. Two patients developed proximal humerus fractures, of which 1 had osseous changes through which the fracture occurred.
Discussion: RTSA+LDT may place the proximal humeral cortex at greater risk than previously described. Using a long-stem prosthesis in the setting of RTSA+LDT may limit the consequences of this complication
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
The Demographics, Stellar Populations, and Star Formation Histories of Fast Radio Burst Host Galaxies: Implications for the Progenitors
We present a comprehensive catalog of observations and stellar population
properties for 23 highly secure host galaxies of fast radio bursts (FRBs). Our
sample comprises six repeating FRBs and 17 apparent non-repeaters. We present
82 new photometric and eight new spectroscopic observations of these hosts.
Using stellar population synthesis modeling and employing non-parametric star
formation histories (SFHs), we find that FRB hosts have a median stellar mass
of , mass-weighted age Gyr, and
ongoing star formation rate yr but span wide
ranges in all properties. Classifying the hosts by degree of star formation, we
find that 87% (20/23 hosts) are star-forming, two are transitioning, and one is
quiescent. The majority trace the star-forming main sequence of galaxies, but
at least three FRBs in our sample originate in less active environments (two
non-repeaters and one repeater). Across all modeled properties, we find no
statistically significant distinction between the hosts of repeaters and
non-repeaters. However, the hosts of repeating FRBs generally extend to lower
stellar masses, and the hosts of non-repeaters arise in more optically luminous
galaxies. While four of the galaxies with the most clear and prolonged rises in
their SFHs all host repeating FRBs, demonstrating heightened star formation
activity in the last Myr, one non-repeating host shows this SFH
as well. Our results support progenitor models with short delay channels (i.e.,
magnetars formed via core-collapse supernova) for most FRBs, but the presence
of some FRBs in less active environments suggests a fraction form through more
delayed channels.Comment: 52 pages, 32 figures, 6 tables, submitte
Search for gravitational wave bursts in LIGO's third science run
We report on a search for gravitational wave bursts in data from the three
LIGO interferometric detectors during their third science run. The search
targets subsecond bursts in the frequency range 100-1100 Hz for which no
waveform model is assumed, and has a sensitivity in terms of the
root-sum-square (rss) strain amplitude of hrss ~ 10^{-20} / sqrt(Hz). No
gravitational wave signals were detected in the 8 days of analyzed data.Comment: 12 pages, 6 figures. Amaldi-6 conference proceedings to be published
in Classical and Quantum Gravit
Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides LiFe(OH)FeSe
Hydrothermal synthesis is described of layered lithium iron selenide hydroxides LiFex(OH)FeSe (x0.2; 0.02 < < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low ( < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the LiFe(OH) reservoir layer to fill vacancies in the selenide layer
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