975 research outputs found
Different Modulation of the Cortical Silent Period by Two Phases of Short Interval Intracortical Inhibition
PURPOSE:
To investigate the influence of 2 phases of short interval intracortical inhibition (SICI) on the cortical silent period (SP).
MATERIALS AND METHODS:
Single- and paired-pulse transcranial magnetic stimulations (TMSs) at 1 and 2.5ms interstimulus intervals (ISIs) were applied to the left motor cortex in 12 healthy subjects while their right hand muscles were moderately activated. Conditioning stimulation intensity was 90% of the active motor threshold (AMT). Test stimulation intensities were 120, 140, 160, 180, 200, 220, 240, 260% of the AMT and at 100% of the maximal stimulator output, the order of which was arranged randomly. The rectified electromyography area of motor evoked potential (MEP) and duration of the SP were measured off-line using a computerized program.
RESULTS:
At high-test stimulation intensities, MEP areas were saturated in both single- and paired-pulse stimulations, except that saturated MEPs were smaller for the paired-pulse TMS at 1ms ISI than for the other conditions. As the test stimulation intensity increased, SP was progressively prolonged in both single- and paired-pulse stimulations but was shorter in paired-pulse than single-pulse TMS. Overall, the ratio of SP duration/MEP area was comparable between single- and paired-pulse TMS except for the paired-pulse TMS at 1 ms ISI with a test stimulation intensity at 140-180% of the AMT, in which the ratio was significantly higher than in the single pulse TMS.
CONCLUSION:
These results suggest that 2 phases of SICI modulate MEP saturation and SP duration differently and provide additional evidence supporting the view that 2 phases of SICI are mediated by different inhibitory mechanisms.ope
PAGaN I: Multi-Frequency Polarimetry of AGN Jets with KVN
Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to
study the structure of and physical conditions in relativistic outflows. For
such studies, multi-frequency polarimetric very long baseline interferometric
(VLBI) observations are important as they directly probe particle densities,
magnetic field geometries, and several other parameters. We present results
from first-epoch data obtained by the Korean VLBI Network (KVN) within the
frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We
observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129
GHz in dual polarization mode. Our observations constrain apparent brightness
temperatures of jet components and radio cores in our sample to K
and K, respectively. Degrees of linear polarization are
relatively low overall: less than 10%. This indicates suppression of
polarization by strong turbulence in the jets. We found an exceptionally high
degree of polarization in a jet component of BL Lac at 43 GHz, with 40%. Assuming a transverse shock front propagating downstream along the
jet, the shock front being almost parallel to the line of sight can explain the
high degree of polarization.Comment: 14 pages, 17 figures, 4 tables. To appear in JKAS (received 2015 July
27; accepted 2015 October 25). Note the PAGaN II companion paper by J. Oh et
a
PAGaN II: The Evolution of AGN Jets on Sub-Parsec Scales
We report first results from KVN and VERA Array (KaVA) VLBI observations
obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN)
project. We observed eight selected AGN at 22 and 43 GHz in single polarization
(LCP) between March 2014 and April 2015. Each source was observed for 6 to 8
hours per observing run to maximize the coverage. We obtained a total of
15 deep high-resolution images permitting the identification of individual
circular Gaussian jet components and three spectral index maps of BL Lac, 3C
111 and 3C 345 from simultaneous dual-frequency observations. The spectral
index maps show trends in agreement with general expectations -- flat core and
steep jets -- while the actual value of the spectral index for jets shows
indications for a dependence on AGN type. We analyzed the kinematics of jet
components of BL Lac and 3C 111, detecting superluminal proper motions with
maximum apparent speeds of about . This constrains the lower limits of the
intrinsic component velocities to and the upper limits of the angle
between jet and line of sight to 20. In agreement with global jet
expansion, jet components show systematically larger diameters at larger
core distances , following the global relation , albeit within
substantial scatter.Comment: 13 pages, 15 figures, 4 tables. To appear in JKAS (received 2015
August 31; accepted 2015 October 15). Note the PAGaN I companion paper by
J.-Y. Kim et a
The Globular Cluster System of M60 (NGC 4649). I. CFHT MOS Spectroscopy and Database
We present the measurement of radial velocities for globular clusters in M60,
giant elliptical galaxy in the Virgo cluster. Target globular cluster
candidates were selected using the Washington photometry based on the deep
16\arcmin \times 16\arcmin images taken at the KPNO 4m and using the
photometry derived from the HST/WFPC2 archive images. The spectra of the target
objects were obtained using the Multi-Object Spectrograph (MOS) at the
Canada-France-Hawaii Telescope (CFHT). We have measured the radial velocity for
111 objects in the field of M60: 93 globular clusters (72 blue globular
clusters with and 21 red globular clusters with
), 11 foreground stars, 6 small galaxies, and the nucleus of
M60. The measured velocities of the 93 globular clusters range from
km s to km s, with a mean value of
km s, which is in good agreement with the velocity of the nucleus of M60
( km s). Combining our results with data in the
literature, we present a master catalog of radial velocities for 121 globular
clusters in M60. The velocity dispersion of the globular clusters in the master
catalog is found to be km s for the entire sample,
km s for 83 blue globular clusters, and
km s for 38 red globular clusters.Comment: 29 pages, 8 figures. To appear in Ap
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster (GC) system in the
giant elliptical galaxy (gE) M60 in the Virgo cluster. Using the photometric
and spectroscopic database of 121 GCs (83 blue GCs and 38 red GCs), we have
investigated the kinematics of the GC system. We have found that the M60 GC
system shows a significant overall rotation. The rotation amplitude of the blue
GCs is slightly smaller than or similar to that of the red GCs, and their
angles of rotation axes are similar. The velocity dispersions about the mean
velocity and about the best fit rotation curve for the red GCs are marginally
larger than those for the blue GCs. Comparison of observed stellar and GC
velocity dispersion profiles with those calculated from the stellar mass
profile shows that the mass-to-light ratio should be increased as the
galactocentric distance increases, indicating the existence of an extended dark
matter halo. The entire sample of GCs in M60 is found to have a tangentially
biased velocity ellipsoid unlike the GC systems in other gEs. Two subsamples
appear to have different velocity ellipsoids. The blue GC system has a modest
tangentially biased velocity ellipsoid, while the red GC system has a modest
radially biased or an isotropic velocity ellipsoid. From the comparison of the
kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC
1399, NGC 5128, and NGC 4636), it is found that the velocity dispersion of the
blue GC system is similar to or larger than that of the red GC system except
for M60, and the rotation of the GC system is not negligible. The entire sample
of each GC system shows an isotropic velocity ellipsoid except for M60, while
the subsamples show diverse velocity ellipsoids. We discuss the implication of
these results for the formation models of the GC system in gEs.Comment: 48 pages, 16 figures. To appear in Ap
Mechanisms and energetics of free radical initiated disulfide bond cleavage in model peptides and insulin by mass spectrometry
We investigate the mechanism of disulfide bond cleavage in gaseous peptide and protein ions initiated by a covalently-attached regiospecific acetyl radical using mass spectrometry (MS). Highly selective S–S bond cleavages with some minor C–S bond cleavages are observed by a single step of collisional activation. We show that even multiple disulfide bonds in intact bovine insulin are fragmented in the MS2 stage, releasing the A- and B-chains with a high yield, which has been challenging to achieve by other ion activation methods. Yet, regardless of the previous reaction mechanism studies, it has remained unclear why (1) disulfide bond cleavage is preferred to peptide backbone fragmentation, and why (2) the S–S bond that requires the higher activation energy conjectured in previously suggested mechanisms is more prone to be cleaved than the C–S bond by hydrogen-deficient radicals. To probe the mechanism of these processes, model peptides possessing deuterated β-carbon(s) at the disulfide bond are employed. It is suggested that the favored pathway of S–S bond cleavage is triggered by direct acetyl radical attack at sulfur with concomitant cleavage of the S–S bond (S_H2). The activation energy for this process is substantially lower by ~9–10 kcal mol^(−1) than those of peptide backbone cleavage processes determined by density functional quantum chemical calculations. Minor reaction pathways are initiated by hydrogen abstraction from the α-carbon or the β-carbon of a disulfide, followed by β-cleavages yielding C–S or S–S bond scissions. The current mechanistic findings should be generally applicable to other radical-driven disulfide bond cleavages with different radical species such as the benzyl and methyl pyridyl radicals
Necrotizing fasciitis involving the chest and abdominal wall caused by Raoultella planticola
<p>Abstract</p> <p>Background</p> <p><it>Raoultella planticola </it>was originally considered to be a member of environmental <it>Klebsiella</it>. The clinical significance of <it>R. planticola </it>is still not well known.</p> <p>Case presentation</p> <p>We describe the first case of necrotizing fasciitis involving the chest and abdominal wall caused by <it>R. planticola</it>. The identity of the organism was confirmed using 16S rRNA sequencing. The patient was successfully treated with the appropriate antibiotics combined with operative drainage and debridement.</p> <p>Conclusions</p> <p><it>R. planticola </it>had been described as environmental species, but should be suspected in extensive necrotizing fasciitis after minor trauma in mild to moderate immunocompromised patients.</p
Sleep experiences during different lifetime periods and in vivo Alzheimer pathologies
Background
Very little is known for the direction or causality of the relationship between lifetime sleep experiences and in vivo Alzheimers disease (AD) pathologies. This study aimed to examine the relationship between sleep experiences during the young adulthood, midlife, and late-life periods and in vivo cerebral beta-amyloid (Aβ) deposition and AD signature regional neurodegeneration in cognitively normal (CN) old adults.
Methods
This study included 202 CN old adults who participated in the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimers Disease (KBASE) study. All participants underwent a comprehensive clinical assessment, [11C] Pittsburgh Compound B positron emission tomography (PET), [18F] Fluorodeoxyglucose-PET, and magnetic resonance imaging. The quality and duration of sleep were assessed for the following age periods: 20–30s, 40–50s, and the most recent month. All analyses were adjusted for age, gender, education, apolipoprotein E ε4 status, vascular risk score, Hamilton Depression Rating Scale score, and use of sleep medication.
Results
Bad sleep quality and short sleep duration during midlife were significantly associated with increased Aβ deposition and AD signature regional hypometabolism, respectively. Although current bad sleep quality appeared to be associated with increased Aβ accumulation, this association disappeared after controlling for the effects of midlife sleep quality. Neither the quality nor duration of sleep during young adulthood was related to Aβ burden or neurodegeneration.
Conclusions
Bad sleep quality during midlife increases pathological Aβ deposition in the brain, while short sleep duration during the same period accelerates regional hypometabolism.This study was supported by a grant from the Ministry of Science, ICT, and Future Planning, Republic of Korea (Grant No: NRF-2014M3C7A1046042) and a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (Grant No: HI18C0630). The funding source had no role in the design of the study; collection, analysis, and interpretation of the data; and writing of the manuscript
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