867 research outputs found
Intention Tremor and Deficits of Sensory Feedback Control in Multiple Sclerosis: a Pilot Study
Background
Intention tremor and dysmetria are leading causes of upper extremity disability in Multiple Sclerosis (MS). The development of effective therapies to reduce tremor and dysmetria is hampered by insufficient understanding of how the distributed, multi-focal lesions associated with MS impact sensorimotor control in the brain. Here we describe a systems-level approach to characterizing sensorimotor control and use this approach to examine how sensory and motor processes are differentially impacted by MS. Methods
Eight subjects with MS and eight age- and gender-matched healthy control subjects performed visually-guided flexion/extension tasks about the elbow to characterize a sensory feedback control model that includes three sensory feedback pathways (one for vision, another for proprioception and a third providing an internal prediction of the sensory consequences of action). The model allows us to characterize impairments in sensory feedback control that contributed to each MS subject’s tremor. Results
Models derived from MS subject performance differed from those obtained for control subjects in two ways. First, subjects with MS exhibited markedly increased visual feedback delays, which were uncompensated by internal adaptive mechanisms; stabilization performance in individuals with the longest delays differed most from control subject performance. Second, subjects with MS exhibited misestimates of arm dynamics in a way that was correlated with tremor power. Subject-specific models accurately predicted kinematic performance in a reach and hold task for neurologically-intact control subjects while simulated performance of MS patients had shorter movement intervals and larger endpoint errors than actual subject responses. This difference between simulated and actual performance is consistent with a strategic compensatory trade-off of movement speed for endpoint accuracy. Conclusions
Our results suggest that tremor and dysmetria may be caused by limitations in the brain’s ability to adapt sensory feedback mechanisms to compensate for increases in visual information processing time, as well as by errors in compensatory adaptations of internal estimates of arm dynamics
Chandra Early-Type Galaxy Atlas
The hot ISM in early type galaxies (ETGs) plays a crucial role in
understanding their formation and evolution. The structural features of the hot
gas identified by Chandra observations point to key evolutionary mechanisms,
(e.g., AGN and stellar feedback, merging history). In our Chandra Galaxy Atlas
(CGA) project, taking full advantage of the Chandra capabilities, we
systematically analyzed the archival Chandra data of 70 ETGs and produced
uniform data products for the hot gas properties. The primary data products are
spatially resolved 2D spectral maps of the hot gas from individual galaxies. We
emphasize that new features can be identified in the spectral maps which are
not readily visible in the surface brightness maps. The high-level images can
be viewed at the dedicated CGA website, and the CGA data products can be
downloaded to compare with data at other wavelengths and to perform further
analyses. Utilizing our data products, we address a few focused science topics.Comment: 52 pages, 9 figures, accepted in ApJ Supp
Endovascular Therapy for Chronic Cerebrospinal Venous Insufficiency in Multiple Sclerosis
Recent reports have emerged suggesting that multiple sclerosis (MS) may be due to abnormal venous outflow from the central nervous system, termed chronic cerebrospinal venous insufficiency (CCSVI). These reports have generated strong interest and controversy over the prospect of a treatable cause of this chronic debilitating disease. This review aims to describe the proposed association between CCSVI and MS, summarize the current data, and discuss the role of endovascular therapy and the need for rigorous randomized clinical trials to evaluate this association and treatment
DNA Origami Rotaxanes: Tailored Synthesis and Controlled Structure Switching
Mechanically interlocked supramolecular assemblies are appealing building blocks for creating functional nanodevices. Herein, we describe the multistep assembly of large DNA origami rotaxanes that are capable of programmable structural switching. We validated the topology and structural integrity of these rotaxanes by analyzing the intermediate and final products of various assembly routes by electrophoresis and electron microscopy. We further analyzed two structureâ switching behaviors of our rotaxanes, which are both mediated by DNA hybridization. In the first mechanism, the translational motion of the macrocycle can be triggered or halted at either terminus. In the second mechanism, the macrocycle can be elongated after completion of the rotaxane assembly, giving rise to a unique structure that is otherwise difficult to access.A new set of threads: Rotaxanes with a length of up to 200â nm were assembled by a DNA origami approach. The threaded macrocycles can be programmably docked at either dumbbell stopper, and the assemblies can be reconfigured to generate new, otherwise unfavorable rotaxane topologies.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137326/1/anie201604621_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137326/2/anie201604621-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137326/3/anie201604621.pd
One-pot Synthesis of Lactams Using Domino Reactions: Combination of Schmidt Reaction with Sakuri and Aldol Reaction
A series of domino reactions in which the intramolecular Schmidt reaction is combined with either a Sakurai reaction, an aldol reaction, or both is reported. The Sakurai reaction of an allylsilane with an azido-containing enone under Lewis acidic conditions followed by protonation of the resulting titanium enolate species allowed for a subsequent intramolecular Schmidt reaction. Alternatively, the intermediate titanium enolate could undergo an aldol reaction, followed by the intramolecular Schmidt reaction to form lactam products with multiple stereogenic centers. The stereochemical features of the titanium enolate aldol reaction with several 3-azidoaldehyde substrates during this domino process is discussed
Determinants of low bone mineral density in people with multiple sclerosis: Role of physical activity
Background
People with multiple sclerosis (PwMS) have reduced bone mineral density (BMD), but the causes are unclear. Some factors that may cause reduced BMD in PwMS have been understudied, including physical activity, inflammation, cortisol, symptomatic fatigue, and depression. The aim of this study was to investigate factors that may uniquely contribute to reduced BMD in PwMS as compared to people without MS. We hypothesized that physical activity would be the primary determinant of low BMD in PwMS, with additional contributions from inflammation and sympathetic nervous system activation. Methods
We tested 23 PwMS (16 women; median EDSS: 2) and 22 control participants (16 women). BMD was measured from the femoral neck and lumbar spine with dual x-ray absorptiometry. Disability was measured with the Expanded Disability Status Scale, and functional capacity was measured with the Multiple Sclerosis Functional Composite. Questionnaires measured symptomatic fatigue and depression. A blood draw was used to measure calcium, phosphate, vitamin D, N-terminal telopeptide, osteopontin, and cytokine markers of inflammation. Physical activity was measured with accelerometry. Salivary cortisol and cardiac heart rate variability also were obtained. All outcome variables were compared between groups with independent samples t-tests. Variables that were different between groups and significantly correlated (Pearson product-moment) with femoral neck BMD, were included in a theoretical model to explain femoral neck BMD. The expected direction of relations in the theoretical model were developed based upon the results of previous research. A Bayesian path analysis was used to test the relations of predictive variables with femoral neck BMD and interrelations among predictive variables, as detailed in the theoretical model. Results
PwMS had lower BMD at the femoral neck than controls (p = =0.04; mean difference: -0.09; 95% CI: -0.2, -0.004; Cohen\u27s d = =0.65), and there was a smaller, statistically non-significant difference in BMD at the lumbar spine (p = =0.07; mean difference: -0.08; 95% CI: -0.17, 0.007; Cohen\u27s d = =0.59). PwMS also had lower functional capacity (p ≤ 0.001; Cohen\u27s d = =1.50), greater fatigue (pd = =1.88), greater depression (pd = =1.31), and decreased physical activity (p = =0.03; Cohen\u27s d = =0.62). Using path analysis to test our theoretical model, we found that disability (standardized estimate= -0.17), physical activity (standardized estimate=0.39), symptomatic fatigue (standardized estimate= -0.36), depression (standardized estimate= -0.30), and inflammatory markers (standardized estimate=0.27) explained 51% of the variance in femoral neck BMD. Inflammatory markers were also predictive of disability (standardized estimate=0.44) and physical activity (standardized estimate= -0.40). Symptomatic fatigue and depression were correlated (r = =0.64). Conclusion
Physical activity, symptomatic fatigue, depression, disability, and inflammation all contributed independently to decreased femoral neck BMD in PWMS. Bone metabolism in PwMS is complex. Efforts to increase physical activity and address symptomatic fatigue and depression may improve bone mineral density in PwMS. Future research should investigate the mechanisms through which symptomatic fatigue and depression contribute to reduced BMD in PwMS
Filaments of The Slime Mold Cosmic Web And How They Affect Galaxy Evolution
We present a novel method for identifying cosmic web filaments using the
IllustrisTNG (TNG100) cosmological simulations and investigate the impact of
filaments on galaxies. We compare the use of cosmic density field estimates
from the Delaunay Tessellation Field Estimator (DTFE) and the Monte Carlo
Physarum Machine (MCPM), which is inspired by the slime mold organism, in the
DisPerSE structure identification framework. The MCPM-based reconstruction
identifies filaments with higher fidelity, finding more low-prominence/diffuse
filaments and better tracing the true underlying matter distribution than the
DTFE-based reconstruction. Using our new filament catalogs, we find that most
galaxies are located within 1.5-2.5 Mpc of a filamentary spine, with little
change in the median specific star formation rate and the median galactic gas
fraction with distance to the nearest filament. Instead, we introduce the
filament line density, {\Sigma}fil(MCPM), as the total MCPM overdensity per
unit length of a local filament segment, and find that this parameter is a
superior predictor of galactic gas supply and quenching. Our results indicate
that most galaxies are quenched and gas-poor near high-line density filaments
at z10.5 galaxies is mainly driven by
mass, while lower-mass galaxies are significantly affected by the filament line
density. In high-line density filaments, satellites are strongly quenched,
whereas centrals have reduced star formation, but not gas fraction, at z<=0.5.
We discuss the prospect of applying our new filament identification method to
galaxy surveys with SDSS, DESI, Subaru PFS, etc. to elucidate the effect of
large-scale structure on galaxy formation.Comment: Submitted to ApJ, comments welcome. Data available at
https://github.com/farhantasy/CosmicWeb-Galaxies
FIRST-based survey of Compact Steep Spectrum sources, II. MERLIN and VLA observations of Medium-sized Symmetric Objects
A new sample of candidate Compact Steep Spectrum (CSS) sources that are much
weaker than the CSS source prototypes has been selected from the VLA FIRST
catalogue. MERLIN `snapshot' observations of the sources at 5 GHz indicate that
six of them have an FR II-like morphology, but are not edge-brightened as is
normal for Medium-sized Symmetric Objects (MSOs) and FR IIs. Further
observations of these six sources with the VLA at 4.9 GHz and MERLIN at 1.7
GHz, as well as subsequent full-track observations with MERLIN at 5 GHz of what
appeared to be the two sources of greatest interest are presented. The results
are discussed with reference to the established evolutionary model of CSS
sources being young but in which not all of them evolve to become old objects
with extended radio structures. A lack of stable fuelling in some of them may
result in an early transition to a so-called coasting phase so that they fade
away instead of growing to become large-scale objects. It is possible that one
of the six sources (1542+323) could be labelled as a prematurely `dying' MSO or
a `fader'.Comment: 13 pages, matches the version printed in Astronomy & Astrophysic
- …