3,475 research outputs found
Sustained attention training reduces spatial bias in Parkinson’s disease: a pilot case series
Individuals with Parkinson’s disease (PD) commonly demonstrate lateralized spatial biases, which affect daily functioning. Those with PD with initial motor symptoms on the left body side (LPD) have reduced leftward attention, whereas PD with initial motor symptoms on the right side (RPD) may display reduced rightward attention. We investigated whether a sustained attention training program could help reduce these spatial biases. Four non-demented individuals with PD (2 LPD, 2 RPD) performed a visual search task before and after 1 month of computer training. Before training, all participants showed a significant spatial bias and after training, all participants’ spatial bias was eliminated.Published versio
Star Formation in Orion's L1630 Cloud: an Infrared and Multi-epoch X-ray Study
X-ray emission is characteristic of young stellar objects (YSOs) and is known
to be highly variable. We investigate, via an infrared and multi-epoch X-ray
study of the L1630 dark cloud, whether and how X-ray variability in young
stellar objects is related to protostellar evolutionary state. We have analyzed
11 Chandra X-ray Observatory observations, obtained over the course of four
years and totaling ~240 ks exposure time, targeting the eruptive Class I YSO
V1647 Ori in L1630. We used 2MASS and Spitzer data to identify and classify IR
counterparts to L1630 X-ray sources and identified a total of 52 X-ray emitting
YSOs with IR counterparts, including 4 Class I sources and 1 Class 0/I source.
We have detected cool (< 3 MK) plasma, possibly indicative of accretion shocks,
in three classical T Tauri stars. A subsample of 27 X-ray-emitting YSOs were
covered by 9 of the 11 Chandra observations targeting V1647 Ori and vicinity.
For these 27 YSOs, we have constructed X-ray light curves spanning
approximately four years. These light curves highlight the variable nature of
pre-main sequence X-ray emitting young stars; many of the L1630 YSOs vary by
orders of magnitude in count rate between observations. We discuss possible
scenarios to explain apparent trends between various X-ray spectral properties,
X-ray variance and YSO classification.Comment: Accepted for publication in ApJS; 52 pages, 20 figure
X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori
We report a periodicity of ~1 day in the highly elevated X-ray emission from
the protostar V1647 Ori during its two recent multiple-year outbursts of mass
accretion. This periodicity is indicative of protostellar rotation at
near-breakup speed. Modeling of the phased X-ray light curve indicates the
high-temperature (~50 MK), X-ray-emitting plasma, which is most likely heated
by accretion-induced magnetic reconnection, resides in dense (>~5e10 cm-3),
pancake-shaped magnetic footprints where the accretion stream feeds the newborn
star. The sustained X-ray periodicity of V1647 Ori demonstrates that such
protostellar magnetospheric accretion configurations can be stable over
timescales of years.Comment: 26 pages, 10 figure
Unveiling clones and integrons dynamics associated with carbapenemase-producing P. aeruginosa clinical isolates in a portuguese hospital
[Excerpt] Particular epidemic lineages (e.g. 235, 111, ST175 and 244) are associated with carbapenemase-producing P. aeruginosa (CPPA) isolates causing infections. Due to limited therapeutic options and possible carbapenemase spread, CPPA infections are of great concern. Nevertheless, the occurrence, genetic background and clonal dynamics over a long period of time of CPPA strains in Portuguese hospitals are unknown. The study aimed to assess the occurrence and the genetic background of CPPA isolates obtained from a Portuguese University Hospital. Carbapenem-resistant P. aeruginosa isolates obtained from different biological samples from inpatients attending the Hospital Geral de Santo António, Porto during 2006 (n=27) and 2011-3 (n=135) were included. Carbapenemase production was searched by Blue-Carba. Carbapenemase and associated integrons were characterized by PCRs and sequencing. Antimicrobial susceptibility was performed by disc diffusion, E-test and agar dilution methods. Clonality was assessed by MLST. The bla genes location was assessed by I-CeuI/ S1 PFGE and hybridization with specific probes. Plasmid analysis included identification of incompatibility groups by PCR and electrotransformation of P. aeruginosa PAO1. [...
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Suzaku Observation of Strong Fluorescent Iron Line Emission from the Young Stellar Object V1647 Ori during Its New X-ray Outburst
The Suzaku X-ray satellite observed the young stellar object V1647 Ori on 2008 October 8 during the new mass accretion outburst reported in August 2008. During the 87 ksec observation with a net exposure of 40 ks, V1647 Ori showed a. high level of X-ray emission with a gradual decrease in flux by a factor of 5 and then displayed an abrupt flux increase by an order of magnitude. Such enhanced X-ray variability was also seen in XMM-Newton observations in 2004 and 2005 during the 2003-2005 outburst, but has rarely been observed for other young stellar objects. The spectrum clearly displays emission from Helium-like iron, which is a signature of hot plasma (kT approx.5 keV). It also shows a fluorescent iron Ka line with a remarkably large equivalent width of approx. 600 eV. Such a, large equivalent width indicates that a part of the incident X-ray emission that irradiates the circumstellar material and/or the stellar surface is hidden from our line of sight. XMM-Newton spectra during the 2003-2005 outburst did not show a strong fluorescent iron Ka line ; so that the structure of the circumstellar gas very close to the stellar core that absorbs and re-emits X-ray emission from the central object may have changed in between 2005 and 2008. This phenomenon may be related to changes in the infrared morphology of McNeil's nebula between 2004 and 2008
Detection of a Cool, Accretion-Shock-Generated X-Ray Plasma in EX Lupi During the 2008 Optical Eruption
EX Lupi is the prototype for a class of young, pre-main-sequence stars which are observed to undergo irregular, presumably accretion-generated, optical outbursts that result in a several magnitude rise of the optical flux. EX Lupi was observed to optically erupt in 2008 January, triggering Chandra ACIS Target of Opportunity observations shortly thereafter. We find very strong evidence that most of the X-ray emission in the first few months after the optical outburst is generated by accretion of circumstellar material onto the stellar photosphere. Specifically, we find a strong correlation between the decreasing optical and X-ray fluxes following the peak of the outburst in the optical, which suggests that these observed declines in both the optical and X-ray fluxes are the result of declining accretion rate. In addition, in our models of the X-ray spectrum, we find strong evidence for an approx 0.4 keV plasma component, as expected for accretion shocks on low-mass, pre-main-sequence stars. From 2008 March through October, this cool plasma component appeared to fade as EX Lupi returned to its quiescent level in the optical, consistent with a decrease in the overall emission measure of accretion-shock-generated plasma. The overall small increase of the X-ray flux during the optical outburst of EX Lupi is similar to what was observed in previous X-ray observations of the 2005 optical outburst of the EX Lupi-type star V1118 Ori but contrasts with the large increase of the X-ray flux from the erupting young star V1647 Ori during its 2003 and 2008 optical outbursts
Optical Spectroscopy of the Surface Population of the rho Ophiuchi Molecular Cloud: The First Wave of Star Formation
We present the results of optical spectroscopy of 139 stars obtained with the
Hydra multi-object spectrograph. The objects extend over a 1.3 square degree
area surrounding the main cloud of the rho Oph complex. The objects were
selected from narrowband images to have H alpha in emission. Using the presence
of strong H alpha emission, lithium absorption, location in the
Hertzsprung-Russell diagram, or previously reported x-ray emission, we were
able to identify 88 objects as young stars associated with the cloud. Strong H
alpha emission was confirmed in 39 objects with line widths consistent with
their origin in magnetospheric accretion columns. Two of the strongest
emission-line objects are young, x-ray emitting brown dwarf candidates with M8
spectral types. Comparisons of the bolometric luminosities and effective
temperatures with theoretical models suggest a medianage for this population of
2.1 Myr which is signifcantly older than the ages derived for objects in the
cloud core. It appears that these stars formed contemporaneously with low mass
stars in the Upper Scorpius subgroup, likely triggered by massive stars in the
Upper-Centaurus subgroup.Comment: 35 pages of postscript which includes seven figures (some of which
are multi-panel) and four postscript tables. Astronomical Journal (in press
Understanding the DayCent model: Calibration, sensitivity, and identifiability through inverse modeling
AbstractThe ability of biogeochemical ecosystem models to represent agro-ecosystems depends on their correct integration with field observations. We report simultaneous calibration of 67 DayCent model parameters using multiple observation types through inverse modeling using the PEST parameter estimation software. Parameter estimation reduced the total sum of weighted squared residuals by 56% and improved model fit to crop productivity, soil carbon, volumetric soil water content, soil temperature, N2O, and soil NO3− compared to the default simulation. Inverse modeling substantially reduced predictive model error relative to the default model for all model predictions, except for soil NO3− and NH4+. Post-processing analyses provided insights into parameter–observation relationships based on parameter correlations, sensitivity and identifiability. Inverse modeling tools are shown to be a powerful way to systematize and accelerate the process of biogeochemical model interrogation, improving our understanding of model function and the underlying ecosystem biogeochemical processes that they represent
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