14,402 research outputs found
Effects of orthostatic hypotension on cognition in Parkinson's disease
OBJECTIVE: To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in Parkinson disease (PD) using a cross-sectional and within-group design.
METHODS: Individuals without dementia with idiopathic PD included 18 with OH (PDOH) and 19 without OH; 18 control participants were also included. Neuropsychological tests were conducted in supine and upright-tilted positions. Blood pressure was assessed in each posture.
RESULTS: The PD groups performed similarly while supine, demonstrating executive dysfunction in sustained attention and response inhibition, and reduced semantic fluency and verbal memory (encoding and retention). Upright posture exacerbated and broadened these deficits in the PDOH group to include phonemic fluency, psychomotor speed, and auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, with the PDOH group exhibiting a wider range of deficits in executive function and memory as well as significant changes in visuospatial function.
CONCLUSIONS: Cognitive deficits in PD have been widely reported with assessments performed in the supine position, as seen in both our PD groups. Here we demonstrated that those with PDOH had transient, posture-mediated changes in excess of those found in PD without OH. These observed changes suggest an acute, reversible effect. Understanding the effects of OH due to autonomic failure on cognition is desirable, particularly as neuroimaging and clinical assessments collect data only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with OH has quality of life implications, and OH presents itself as a possible target for intervention in cognitive disturbance.Accepted manuscriptAccepted manuscrip
Author response: Effects of orthostatic hypotension on cognition in Parkinson disease
OBJECTIVE: To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in persons with Parkinson's disease (PD) without dementia.
METHODS: There were 55 participants: 37 non-demented individuals with idiopathic PD, including 18 with OH (PDOH), and 19 without (PDWOH), and18 control participants (C). All participants completed neuropsychological tests in the supine and in the upright tilted position. Blood pressure was assessed in each posture using a standardized oscillometric cuff at the right brachial artery.
RESULTS: The two PD groups performed similarly while supine, with a profile notable for executive dysfunction consisting of deficits in sustained attention, response inhibition, and semantic verbal fluency, as well as reduced verbal memory encoding and retention. When upright, these deficits were exacerbated and broadened to include additional cognitive functions in the PDOH group: deficits in phonemic verbal fluency, psychomotor speed, and both basic and complex aspects of auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, though the PDOH group had a wider range of deficits in the executive functioning and memory domains and was the only group to show significant changes in visuospatial skills.
CONCLUSIONS: Cognitive deficits in idiopathic PD have been widely reported, though assessments are typically performed in the supine position. While both PD groups had supine deficits that aligned with prior studies and clinical findings, we demonstrated that those with PD and orthostatic hypotension had transient, posture-mediated changes in excess of those found in PD without autonomic failure. These observed changes suggest an acute, reversible effect, and as orthostatic hypotension is a significant comorbid factor in PD, an independent target for clinical intervention. Further understanding of the effects of autonomic failure on cognition in other disorders is desirable, particularly in the context of neuroimaging studies and clinical assessments where data are collected only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with autonomic failure also has implications for functional activities of daily living and overall quality of life.Accepted manuscrip
Detection, photometry and slitless radial velocities of 535 planetary nebulae in the flattened elliptical galaxy NGC 4697
We have detected 535 planetary nebulae (PNs) in NGC 4697, using the classic
on-band, off-band filter technique with the Focal Reducer and Spectrograph
(FORS) at the Cassegrain focus of the first 8-meter telescope unit of the ESO
Very Large Telescope. From our photometry we have built the [O III] 5007
planetary nebula luminosity function (PNLF) of NGC 4697. It indicates a
distance of 10.5 Mpc, substantially smaller than a previous estimate of 24 Mpc
used in earlier dynamical studies. The PNLF also provides an estimate of the
specific PN formation rate. Combining the information from on-band images with
PN positions on dispersed, slitless grism images, we have obtained radial
velocities for 531 of the 535 PNs. They provide kinematic information up to a
distance of almost three effective radii from the nucleus. Some rotation is
detected in the outer regions, but the rotation curve of this galaxy appears to
drop beyond one effective radius. Assuming an isotropic velocity distribution,
the velocity dispersion profile is consistent with no dark matter within three
effective radii of the nucleus (however, some dark matter can be present if the
velocity distribution is anisotropic). We obtain a blue mass-to-light ratio of
11. Earlier M/L ratios for NGC 4697 were too small, because of the too large
distance used for their derivation.Comment: 52 pages, 24 Postscript figures, ApJ 2001, in pres
Validity of the activPAL3 activity monitor in people moderately affected by Multiple Sclerosis
Background: Walking is the primary form of physical activity performed by people with Multiple Sclerosis (MS), therefore it is important to ensure the validity of tools employed to measure walking activity. The aim of this study was to assess the criterion validity of the activPAL3 activity monitor during overground walking in people with MS.\ud
Methods: Validity of the activPAL3 accelerometer was compared to video observation in 20 people moderately affected by MS. Participants walked 20-30m twice along a straight quiet corridor at a comfortable speed.\ud
Results: Inter-rater reliability of video observations was excellent (all intraclass correlations > 0.99). The mean difference (activPAL3- mean of raters) was -4.70 ± 9.09, -4.55 s ± 10.76 and 1.11 s ± 1.11 for steps taken, walking duration and upright duration respectively. These differences represented 8.7, 10.0 and 1.8% of the mean for each measure respectively. The activPAL3 tended to underestimate steps taken and walking duration in those who walked at cadences of ≤ 38 steps/minute by 60% and 47% respectively.\ud
Discussion: The activPAL3 is valid for measuring walking activity in people moderately affected by MS. It is accurate for upright duration regardless of cadence. In participants with slow walking cadences, outcomes of steps taken and walking duration should be interpreted with caution
Project for the analysis of technology transfer Quarterly report, 1 Apr. 1969 - 30 Jun. 1969
Patterns, statistical analyses, and case studies of transfer and utilization of NASA generated technolog
Theory of Coupled Multipole Moments Probed by X-ray Scattering in CeB
A minimal model for multipole orders in CeB shows that degeneracy of the
quadrupole order parameters and strong spin-orbit coupling lead to peculiar
temperature and magnetic-field dependences of the X-ray reflection intensity at
superlattice Bragg points. Furthermore, the intensity depends sensitively on
the surface direction. These theoretical results explain naturally recent X-ray
experiments in phases II and III of CeB. It is predicted that under weak
magnetic field perpendicular to the (111) surface, the reflection intensity
should change non-monotonically as a function of temperature.Comment: 4 pages, 5 figure
Electronic structure and light-induced conductivity in a transparent refractory oxide
Combined first-principles and experimental investigations reveal the
underlying mechanism responsible for a drastic change of the conductivity (by
10 orders of magnitude) following hydrogen annealing and UV-irradiation in a
transparent oxide, 12CaO.7Al2O3, found by Hayashi et al. The charge transport
associated with photo-excitation of an electron from H, occurs by electron
hopping. We identify the atoms participating in the hops, determine the exact
paths for the carrier migration, estimate the temperature behavior of the
hopping transport and predict a way to enhance the conductivity by specific
doping.Comment: 4 pages including 4 figure
Discovery of 9 Ly alpha emitters at redshift z~3.1 using narrow-band imaging and VLT spectroscopy
Narrow-band imaging surveys aimed at detecting the faint emission from the
5007 [O III] line of intracluster planetary nebulae in Virgo also probe high
redshift z=3.1 Ly alpha emitters. Here we report on the spectroscopic
identification of 9 Ly alpha emitters at z=3.13, obtained with the FORS
spectrograph at Unit 1 of the ESO Very Large Telescope (VLT UT1). The spectra
of these high redshift objects show a narrow, isolated Ly alpha emission with
very faint (frequently undetected) continuum, indicating a large equivalent
width. No other features are visible in our spectra. Our Ly alpha emitters are
quite similar to those found by Hu (1998), Cowie & Hu (1998) and Hu et al.
(1998). Using simple population synthesis models, on the assumption that these
sources are regions of star formation, we conclude that the nebulae are nearly
optically thick and must have a very low dust content, in order to explain the
high observed Ly alpha equivalent widths. For the cosmological and star
formation parameters we adopted, the total stellar mass produced would seem to
correspond to the formation of rather small galaxies, some of which are perhaps
destined to merge. The implied star formation density in our sampled comoving
volume is probably somewhat smaller than, but of the same order of magnitude as
the star formation density at z=3 derived by other authors from Lyman-break
galaxy surveys. This result agrees with the expectation that the Ly alpha
emitters are a low-metallicity (or low-dust) tail in a distribution of star
forming regions at high redshifts. Finally, the Ly alpha emitters may
contribute as many H-ionizing photons as QSOs at z=3.Comment: 26 pages, 17 Postscript figures, ApJ in pres
Radiocarbon and blue optically stimulated luminescence chronologies of the Oitavos consolidated dune (Western Portugal)
The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (~20,000 cal BP) than the OSL age measurement (~15,000 yr), while 14C age measurements on the inorganic component and the gastropods produced ages of ~35,000 yr and ~34,000 yr, respectively. Rare-earth
element analyses provide evidence that the gastropods incorporate geological carbonate, making them an unreliable indicator of the age of the paleosol. We propose that the 14C age of the small organic component of the paleosol is also likely to be unreliable due to incorporation of residual material. The OSL age measurement of the upper paleosol (~15,000 yr) is consistent with the age for the base of the dune (~14,500 yr). The younger OSL age for the top of the dune (~12,000 yr) suggests that it was built up by at least 2 sand pulses or that there was a remobilization of material at the top during its evolution, prior to consolidation
Cortical phase transitions, non-equilibrium thermodynamics and the time-dependent Ginzburg-Landau equation
The formation of amplitude modulated and phase modulated assemblies of
neurons is observed in the brain functional activity. The study of the
formation of such structures requires that the analysis has to be organized in
hierarchical levels, microscopic, mesoscopic, macroscopic, each with its
characteristic space-time scales and the various forms of energy, electric,
chemical, thermal produced and used by the brain. In this paper, we discuss the
microscopic dynamics underlying the mesoscopic and the macroscopic levels and
focus our attention on the thermodynamics of the non-equilibrium phase
transitions. We obtain the time-dependent Ginzburg-Landau equation for the
non-stationary regime and consider the formation of topologically non-trivial
structures such as the vortex solution. The power laws observed in functional
activities of the brain is also discussed and related to coherent states
characterizing the many-body dissipative model of brain.Comment: 19 pages, 4 figures, research pape
- …