157 research outputs found
Prospects for cosmic magnification measurements using HI intensity mapping
We investigate the prospects of measuring the cosmic magnification effect by cross-correlating neutral hydrogen intensity mapping (HβI IM) maps with background optical galaxies. We forecast the signal-to-noise ratio for Hβi IM data from SKA1-MID and HIRAX, combined with LSST photometric galaxy samples. We find that, thanks to their different resolutions, SKA1-MID and HIRAX are highly complementary in such an analysis. We predict that SKA1-MID can achieve a detection with a signal-to-noise ratio of βΌ15 on a multipole range of β β² 200, while HIRAX can reach a signal-to-noise ratio of βΌ50 on 200 < β < 2000. We conclude that measurements of the cosmic magnification signal will be possible on a wide redshift range with foreground HβI intensity maps up to z β² 2, while optimal results are obtained when 0.6 β² z β² 1.3
MuSK induces in vivo acetylcholine receptor clusters in a ligand-independent manner
Muscle-specific receptor tyrosine kinase (MuSK) is required for the formation of the neuromuscular junction. Using direct gene transfer into single fibers, MuSK was expressed extrasynaptically in innervated rat muscle in vivo to identify its contribution to synapse formation. Spontaneous MuSK kinase activity leads, in the absence of its putative ligand neural agrin, to the appearance of Ξ΅-subunitβspecific transcripts, the formation of acetylcholine receptor clusters, and acetylcholinesterase aggregates. Expression of kinase-inactive MuSK did not result in the formation of acetylcholine receptor (AChR) clusters, whereas a mutant MuSK lacking the ectodomain did induce AChR clusters. The contribution of endogenous MuSK was excluded by using genetically altered mice, where the kinase domain of the MuSK gene was flanked by loxP sequences and could be deleted upon expression of Cre recombinase. This allowed the conditional inactivation of endogenous MuSK in single muscle fibers and prevented the induction of ectopic AChR clusters. Thus, the kinase activity of MuSK initiates signals that are sufficient to induce the formation of AChR clusters. This process does not require additional determinants located in the ectodomain
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HR outsourcing:The impact on HR's strategic role and remaining in-house HR function
Past research on HR outsourcing (HRO) has offered conflicting views about its impact on HR's strategic position. This study highlights the processes by which decisions to outsource HR are made, followed by the processes implemented post such decisions and their effect on the HR function. Using a case study approach and semi-structured interviews (N = 35) within a German subsidiary of a US MNC, we provide a framework of HR processes seeking to achieve standardization in terms of harmonization of HR activities across the subsidiary. The findings reveal that the effects of outsourcing on in-house HR showed a decrease in flexibility of the HR function, a slowdown in processing time of transactional HR as well as a decrease in satisfaction and work intensification for HR managers. Further, it remains questionable as to whether the function of HR was able to enhance its strategic position through outsourcing
MeerKLASS: MeerKAT Large Area Synoptic Survey
We discuss the ground-breaking science that will be possible with a wide area
survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area
Synoptic Survey). The current specifications of MeerKAT make it a great fit for
science applications that require large survey speeds but not necessarily high
angular resolutions. In particular, for cosmology, a large survey over for hours will potentially provide the first
ever measurements of the baryon acoustic oscillations using the 21cm intensity
mapping technique, with enough accuracy to impose constraints on the nature of
dark energy. The combination with multi-wavelength data will give unique
additional information, such as exquisite constraints on primordial
non-Gaussianity using the multi-tracer technique, as well as a better handle on
foregrounds and systematics. Such a wide survey with MeerKAT is also a great
match for HI galaxy studies, providing unrivalled statistics in the pre-SKA era
for galaxies resolved in the HI emission line beyond local structures at z >
0.01. It will also produce a large continuum galaxy sample down to a depth of
about 5\,Jy in L-band, which is quite unique over such large areas and
will allow studies of the large-scale structure of the Universe out to high
redshifts, complementing the galaxy HI survey to form a transformational
multi-wavelength approach to study galaxy dynamics and evolution. Finally, the
same survey will supply unique information for a range of other science
applications, including a large statistical investigation of galaxy clusters as
well as produce a rotation measure map across a huge swathe of the sky. The
MeerKLASS survey will be a crucial step on the road to using SKA1-MID for
cosmological applications and other commensal surveys, as described in the top
priority SKA key science projects (abridged).Comment: Larger version of the paper submitted to the Proceedings of Science,
"MeerKAT Science: On the Pathway to the SKA", Stellenbosch, 25-27 May 201
HIRAX:A Probe of Dark Energy and Radio Transients
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new
400-800MHz radio interferometer under development for deployment in South
Africa. HIRAX will comprise 1024 six meter parabolic dishes on a compact grid
and will map most of the southern sky over the course of four years. HIRAX has
two primary science goals: to constrain Dark Energy and measure structure at
high redshift, and to study radio transients and pulsars. HIRAX will observe
unresolved sources of neutral hydrogen via their redshifted 21-cm emission line
(`hydrogen intensity mapping'). The resulting maps of large-scale structure at
redshifts 0.8-2.5 will be used to measure Baryon Acoustic Oscillations (BAO).
HIRAX will improve upon current BAO measurements from galaxy surveys by
observing a larger cosmological volume (larger in both survey area and redshift
range) and by measuring BAO at higher redshift when the expansion of the
universe transitioned to Dark Energy domination. HIRAX will complement CHIME, a
hydrogen intensity mapping experiment in the Northern Hemisphere, by completing
the sky coverage in the same redshift range. HIRAX's location in the Southern
Hemisphere also allows a variety of cross-correlation measurements with
large-scale structure surveys at many wavelengths. Daily maps of a few thousand
square degrees of the Southern Hemisphere, encompassing much of the Milky Way
galaxy, will also open new opportunities for discovering and monitoring radio
transients. The HIRAX correlator will have the ability to rapidly and
eXperimentciently detect transient events. This new data will shed light on the
poorly understood nature of fast radio bursts (FRBs), enable pulsar monitoring
to enhance long-wavelength gravitational wave searches, and provide a rich data
set for new radio transient phenomena searches. This paper discusses the HIRAX
instrument, science goals, and current status.Comment: 11 pages, 5 figure
Role of Myosin Va in the Plasticity of the Vertebrate Neuromuscular Junction In Vivo
Background: Myosin Va is a motor protein involved in vesicular transport and its absence leads to movement disorders in humans (Griscelli and Elejalde syndromes) and rodents (e.g. dilute lethal phenotype in mice). We examined the role of myosin Va in the postsynaptic plasticity of the vertebrate neuromuscular junction (NMJ). Methodology/Principal Findings: Dilute lethal mice showed a good correlation between the propensity for seizures, and fragmentation and size reduction of NMJs. In an aneural C2C12 myoblast cell culture, expression of a dominant-negative fragment of myosin Va led to the accumulation of punctate structures containing the NMJ marker protein, rapsyn-GFP, in perinuclear clusters. In mouse hindlimb muscle, endogenous myosin Va co-precipitated with surface-exposed or internalised acetylcholine receptors and was markedly enriched in close proximity to the NMJ upon immunofluorescence. In vivo microscopy of exogenous full length myosin Va as well as a cargo-binding fragment of myosin Va showed localisation to the NMJ in wildtype mouse muscles. Furthermore, local interference with myosin Va function in live wildtype mouse muscles led to fragmentation and size reduction of NMJs, exclusion of rapsyn-GFP from NMJs, reduced persistence of acetylcholine receptors in NMJs and an increased amount of punctate structures bearing internalised NMJ proteins. Conclusions/Significance: In summary, our data show a crucial role of myosin Va for the plasticity of live vertebrate neuromuscular junctions and suggest its involvement in the recycling of internalised acetylcholine receptors back to th
Motor Unit Abnormalities in Dystonia musculorum Mice
Dystonia musculorum (dt) is a mouse inherited sensory neuropathy caused by mutations in the dystonin gene. While the primary pathology lies in the sensory neurons of dt mice, the overt movement disorder suggests motor neurons may also be affected. Here, we report on the contribution of motor neurons to the pathology in dt27J mice. Phenotypic dt27J mice display reduced alpha motor neuron cell number and eccentric alpha motor nuclei in the ventral horn of the lumbar L1 spinal cord region. A dramatic reduction in the total number of motor axons in the ventral root of postnatal day 15 dt27J mice was also evident. Moreover, analysis of the trigeminal nerve of the brainstem showed a 2.4 fold increase in number of degenerating neurons coupled with a decrease in motor neuron number relative to wild type. Aberrant phosphorylation of neurofilaments in the perikaryon region and axonal swellings within the pre-synaptic terminal region of motor neurons were observed. Furthermore, neuromuscular junction staining of dt27J mouse extensor digitorum longus and tibialis anterior muscle fibers showed immature endplates and a significant decrease in axon branching compared to wild type littermates. Muscle atrophy was also observed in dt27J muscle. Ultrastructure analysis revealed amyelinated motor axons in the ventral root of the spinal nerve, suggesting a possible defect in Schwann cells. Finally, behavioral analysis identified defective motor function in dt27J mice. This study reveals neuromuscular defects that likely contribute to the dt27J pathology and identifies a critical role for dystonin outside of sensory neurons
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