30 research outputs found
Simulations of eccentric disks in close binary systems
We study the development of finite eccentricity in accretion disks in close
binary systems using a two-dimensional grid-based numerical scheme. We perform
detailed parameter studies to explore the dependence on viscosity, disk aspect
ratio, the inclusion of a mass-transfer stream and the role of the boundary
conditions. We consider mass ratios 0.05<q<0.3 appropriate to superoutbursting
cataclysmic binary systems.
Instability to the formation of a precessing eccentric disk that attains a
quasi-steady state with mean eccentricity in the range 0.3-0.5 occurs readily.
The shortest growth times are ~15 binary orbits for the largest viscosities and
the instability mechanism is for the most part consistent with the
mode-coupling mechanism associated with the 3:1 resonance proposed by Lubow.
However, the results are sensitive to the treatment of the inner boundary and
to the incorporation of the mass-transfer stream. In the presence of a stream
we found a critical viscosity below which the disk remains circular.
Incorporation of a mass-transfer stream tends to impart stability for small
enough viscosity (or, equivalently, mass-transfer rate through the disk) and
does assist in obtaining a prograde precession rate that is in agreement with
observations. For the larger q the location of the 3:1 resonance is pushed
outwards towards the Roche lobe where higher-order mode couplings and
nonlinearity occur. It is likely that three-dimensional simulations that
properly resolve the disk's vertical structure are required to make significant
progress in this case.Comment: 19 pages, 27 Figures, accepted by A&
SPH Simulations of Negative (Nodal) Superhumps: A Parametric Study
Negative superhumps in cataclysmic variable systems result when the accretion
disc is tilted with respect to the orbital plane. The line of nodes of the
tilted disc precesses slowly in the retrograde direction, resulting in a
photometric signal with a period slightly less than the orbital period. We use
the method of smoothed particle hydrodynamics to simulate a series of models of
differing mass ratio and effective viscosity to determine the retrograde
precession period and superhump period deficit as a function of
system mass ratio . We tabulate our results and present fits to both
and versus , as well as compare the
numerical results with those compiled from the literature of negative superhump
observations. One surprising is that while we find negative superhumps most
clearly in simulations with an accretion stream present, we also find evidence
for negative superhumps in simulations in which we shut off the mass transfer
stream completely, indicating that the origin of the photometric signal is more
complicated than previously believed.Comment: 14 pages, 15 figures. Accepted for publication in MNRA
Proteomics of rimmed vacuoles define new risk allele in inclusion body myositis
OBJECTIVE: Sporadic inclusion body myositis (sIBM) pathogenesis is unknown; however, rimmed vacuoles (RVs) are a constant feature. We propose to identify proteins that accumulate within RVs. METHODS: RVs and intact myofibers were laser microdissected from skeletal muscle of 18 sIBM patients and analyzed by a sensitive mass spectrometry approach using label-free spectral count-based relative protein quantification. Whole exome sequencing was performed on 62 sIBM patients. Immunofluorescence was performed on patient and mouse skeletal muscle. RESULTS: 213 proteins were enriched by >1.5X in RVs compared to controls and included proteins previously reported to accumulate in sIBM tissue or when mutated cause myopathies with RVs. Proteins associated with protein folding and autophagy were the largest group represented. One autophagic adaptor protein not previously identified in sIBM was FYCO1. Rare missense coding FYCO1 variants were present in 11.3% of sIBM patients compared with 2.6% of controls (p=0.003). FYCO1 co-localized at RVs with autophagic proteins such as MAP1LC3 and SQSTM1 in sIBM and other RV myopathies. One FYCO1 variant protein had reduced co-localization with MAP1LC3 when expressed in mouse muscle. INTERPRETATION: This study used an unbiased proteomic approach to identify RV proteins in sIBM that included a novel protein involved in sIBM pathogenesis. FYCO1 accumulates at RVs and rare missense variants in FYCO1 are overrepresented in sIBM patients. These FYCO1 variants may impair autophagic function leading to RV formation in sIBM patient muscle. FYCO1 functionally connects autophagic and endocytic pathways supporting the hypothesis that impaired endolysosmal degradation underlies the pathogenesis of sIBM
Neuromuscular imaging in inherited muscle diseases
Driven by increasing numbers of newly identified genetic defects and new insights into the field of inherited muscle diseases, neuromuscular imaging in general and magnetic resonance imaging (MRI) in particular are increasingly being used to characterise the severity and pattern of muscle involvement. Although muscle biopsy is still the gold standard for the establishment of the definitive diagnosis, muscular imaging is an important diagnostic tool for the detection and quantification of dystrophic changes during the clinical workup of patients with hereditary muscle diseases. MRI is frequently used to describe muscle involvement patterns, which aids in narrowing of the differential diagnosis and distinguishing between dystrophic and non-dystrophic diseases. Recent work has demonstrated the usefulness of muscle imaging for the detection of specific congenital myopathies, mainly for the identification of the underlying genetic defect in core and centronuclear myopathies. Muscle imaging demonstrates characteristic patterns, which can be helpful for the differentiation of individual limb girdle muscular dystrophies. The aim of this review is to give a comprehensive overview of current methods and applications as well as future perspectives in the field of neuromuscular imaging in inherited muscle diseases. We also provide diagnostic algorithms that might guide us through the differential diagnosis in hereditary myopathies
Berberine enhances defects in the establishment of leaf polarity in asymmetric leaves1 and asymmetric leaves2 of Arabidopsis thaliana
Predicting Anxiety Diagnoses and Severity with the CBCL-A: Improvement Relative to Other CBCL Scales?
The Child Behavior Checklist (CBCL) is a widely used parent-report of child and adolescent behavior. We examined the ability of the CBCL-A scale, a previously published subset of CBCL items, to predict the presence of generalized anxiety disorder (GAD), separation anxiety disorder (SAD), and social phobia (SoP), as well as anxiety severity, among 488 youth randomized in the Child Anxiety Multimodal Study (CAMS). We predicted that the CBCL-A’s unique inclusion of items related to somatic symptoms would better identify anxiety disorder and severity than other CBCL scales, given that somatic complaints are often key features of anxiety among youth. Results support the use of the anxiety-based CBCL subscales as first-line screeners for generally elevated symptoms of anxiety, rather than tools to identify specific anxiety disorders. Although somatic symptoms are often reported and included in diagnostic criteria for certain anxiety disorders (e.g., SAD, GAD), the unique combination of somatic and non-somatic symptoms for the CBCL-A subscale did not increase its ability to consistently predict the presence of specific anxiety disorders