2,114 research outputs found
A comparison of resting state functional magnetic resonance imaging to invasive electrocortical stimulation for sensorimotor mapping in pediatric patients
Localizing neurologic function within the brain remains a significant challenge in clinical neurosurgery. Invasive mapping with direct electrocortical stimulation currently is the clinical gold standard but is impractical in young or cognitively delayed patients who are unable to reliably perform tasks. Resting state functional magnetic resonance imaging non-invasively identifies resting state networks without the need for task performance, hence, is well suited to pediatric patients. We compared sensorimotor network localization by resting state fMRI to cortical stimulation sensory and motor mapping in 16 pediatric patients aged 3.1 to 18.6 years. All had medically refractory epilepsy that required invasive electrographic monitoring and stimulation mapping. The resting state fMRI data were analyzed using a previously trained machine learning classifier that has previously been evaluated in adults. We report comparable functional localization by resting state fMRI compared to stimulation mapping. These results provide strong evidence for the utility of resting state functional imaging in the localization of sensorimotor cortex across a wide range of pediatric patients
On the role of the corpus callosum in interhemispheric functional connectivity in humans
Resting state functional connectivity is defined in terms of temporal correlations between physiologic signals, most commonly studied using functional magnetic resonance imaging. Major features of functional connectivity correspond to structural (axonal) connectivity. However, this relation is not one-to-one. Interhemispheric functional connectivity in relation to the corpus callosum presents a case in point. Specifically, several reports have documented nearly intact interhemispheric functional connectivity in individuals in whom the corpus callosum (the major commissure between the hemispheres) never develops. To investigate this question, we assessed functional connectivity before and after surgical section of the corpus callosum in 22 patients with medically refractory epilepsy. Section of the corpus callosum markedly reduced interhemispheric functional connectivity. This effect was more profound in multimodal associative areas in the frontal and parietal lobe than primary regions of sensorimotor and visual function. Moreover, no evidence of recovery was observed in a limited sample in which multiyear, longitudinal follow-up was obtained. Comparison of partial vs. complete callosotomy revealed several effects implying the existence of polysynaptic functional connectivity between remote brain regions. Thus, our results demonstrate that callosal as well as extracallosal anatomical connections play a role in the maintenance of interhemispheric functional connectivity
Simulated impacts of climate change on water use and yield of irrigated sugarcane in South Africa
Reliable predictions of climate change impacts on water use, irrigation requirements and yields of irrigated
sugarcane in South Africa (a water-scarce country) are necessary to plan adaptation strategies. Although previous
work has been done in this regard, methodologies and results vary considerably. The objectives were (1) to
estimate likely impacts of climate change on sugarcane yields, water use and irrigation demand at three irrigated
sugarcane production sites in South Africa (Malelane, Pongola and LaMercy) for current (1980–2010) and future
(2070–2100) climate scenarios, using an approach based on the Agricultural Model Intercomparison and
Improvement Project (AgMIP) protocols; and (2) to assess the suitability of this methodology for investigating
climate change impacts on sugarcane production.
Future climate datasets were generated using the Delta downscaling method and three Global Circulation Models
(GCMs) assuming atmospheric CO2 concentration [CO2] of 734 ppm (A2 emissions scenario). Yield and water use
were simulated using the DSSAT-Canegro v4.5 model.
Irrigated cane yields are expected to increase at all three sites (between 11 and 14%), primarily due to increased
interception of radiation as a result of accelerated canopy development. Evapotranspiration and irrigation
requirements increased by 11% due to increased canopy cover and evaporative demand. Sucrose yields are expected
to decline because of increased consumption of photo-assimilate for structural growth and maintenance
respiration. Crop responses in canopy development and yield formation differed markedly between the crop
cycles investigated.
Possible agronomic implications of these results include reduced weed control costs due to shortened periods of
partial canopy, a need for improved efficiency of irrigation to counter increased demands, and adjustments to
ripening and harvest practices to counter decreased cane quality and optimise productivity.
Although the Delta climate data downscaling method is considered robust, accurate and easily-understood,
it does not change the future number of rain-days per month. The impacts of this and other climate data simplifications
ought to be explored in future work. Shortcomings of the DSSAT-Canegro model include the simulated
responses of phenological development, photosynthesis and respiration processes to high temperatures, and
the disconnect between simulated biomass accumulation and expansive growth. Proposed methodology
refinements should improve the reliability of predicted climate change impacts on sugarcane yield.South African Sugarcane Research Institute (SASRI).http:// www.elsevier.com/ locate/agsy2016-10-31hb201
Extensive error in the number of genes inferred from draft genome assemblies
Current sequencing methods produce large amounts of data, but genome assemblies based on these data are often woefully incomplete. These incomplete and error-filled assemblies result in many annotation errors, especially in the number of genes present in a genome. In this paper we investigate the magnitude of the problem, both in terms of total gene number and the number of copies of genes in specific families. To do this, we compare multiple draft assemblies against higher-quality versions of the same genomes, using several new assemblies of the chicken genome based on both traditional and next-generation sequencing technologies, as well as published draft assemblies of chimpanzee. We find that upwards of 40% of all gene families are inferred to have the wrong number of genes in draft assemblies, and that these incorrect assemblies both add and subtract genes. Using simulated genome assemblies of Drosophila melanogaster, we find that the major cause of increased gene numbers in draft genomes is the fragmentation of genes onto multiple individual contigs. Finally, we demonstrate the usefulness of RNA-Seq in improving the gene annotation of draft assemblies, largely by connecting genes that have been fragmented in the assembly process
Optimized pulses for the control of uncertain qubits
Constructing high-fidelity control fields that are robust to control, system,
and/or surrounding environment uncertainties is a crucial objective for quantum
information processing. Using the two-state Landau-Zener model for illustrative
simulations of a controlled qubit, we generate optimal controls for \pi/2- and
\pi-pulses, and investigate their inherent robustness to uncertainty in the
magnitude of the drift Hamiltonian. Next, we construct a quantum-control
protocol to improve system-drift robustness by combining environment-decoupling
pulse criteria and optimal control theory for unitary operations. By
perturbatively expanding the unitary time-evolution operator for an open
quantum system, previous analysis of environment-decoupling control pulses has
calculated explicit control-field criteria to suppress environment-induced
errors up to (but not including) third order from \pi/2- and \pi-pulses. We
systematically integrate this criteria with optimal control theory,
incorporating an estimate of the uncertain parameter, to produce improvements
in gate fidelity and robustness, demonstrated via a numerical example based on
double quantum dot qubits. For the qubit model used in this work, post facto
analysis of the resulting controls suggests that realistic control-field
fluctuations and noise may contribute just as significantly to gate errors as
system and environment fluctuations.Comment: 38 pages, 15 figures, RevTeX 4.1, minor modifications to the previous
versio
Serum α-Tocopherol Concentration in Relation to Subsequent Colorectal Cancer: Pooled Data From Five Cohorts
Background Numerous monoclonal antibodies (MAbs) have been produced to antigens found in human melanomas. Three of the best characterized melanoma antigens include the melanoma-associated glycoproteins (MAGs) defined by two reagent families—the ME491 family (including ME491, 8-1H, and 8-2A) and the NKI/C-3 family (including NKI/C-3 and NKI/black-13)—as well as the neuroglandular antigen (NGA) defined by MAbs LS59, LS62, and LS140. These three antigens have significant similarities in tissue distribution, biosynthesis, and structure. The ME491 MAG has been cloned, mapped, and sequenced. Numerous non-melanoma-associated proteins (Sm23, CO-029, R2, TAPA-1, CD9, CD37, CD53, and CD63) have recently been shown to have significant homology to this sequence. Purpose We conducted this study to investigate the similarity between the two MAG antigens and NGA. Methods Several reagents defining the three different melanoma antigens were compared, using competition immunoprecipitation, immunoas-say, and inhibition radioimmunoassay techniques. Results Immunoassay experiments show that MAbs defining the three melanoma antigens bind to affinity-purified ME491 antigen and inhibit each other from binding in an inhibition radioimmunoassay. Competition immunoprecipitation ex-periments demonstrate that the ME491 and NKI/C-3 antibodies bind to NGA. Rabbit anti-ME491 idiotype serum recognizes determinants shared by NKI/C-3 and the anti-NGA MAbs. A competition immunoprecipitation experiment also confirms the identity of CD63, as defined by MAb RUU-SP 2.28, with the three melanoma antigens. Conclusion These data indicate that the MAGs defined by ME491 and NKI/C-3 as well as the anti-NGA antibodies are epitopes of the same molecule, which is identical to CD63 by both immunochemical and molecular genetic investigations. Implications Our results indicate that the data obtained in studies of these three melanoma antigens may be pooled, and we propose that the molecule recognized by these reagents be classified as CD63. [J Natl Cancer Inst 84:422-429, 1992
Excretory-secretory products from adult helminth <i>Nippostrongylus brasiliensis</i> have <i>in vitro</i> bactericidal activity
Introduction. Intestinal helminths and microbiota share the same anatomical niche during infection and are likely to interact either directly or indirectly. Whether intestinal helminths employ bactericidal strategies that influence their microbial environment is not completely understood.Hypothesis. In the present study, the hypothesis that the adult hookworm Nippostrongylus brasiliensis produces molecules that impair bacterial growth in vitro, is tested.Aim. To investigate the in vitro bactericidal activity of Nippostrongylus brasiliensis against commensal and pathogenic bacteria.Methodology. The bactericidal effect of somatic extract and excretory-secretory products of adult Nippostrongylus brasiliensis on Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Salmonella enterica serovar Typhimurium, and Klebsiella pneumoniae) bacteria was assessed using growth assays. Minimum inhibitory concentration and minimum bactericidal concentration assays were performed using excretory-secretory products released from the pathogen.Results. Broad-spectrum in vitro bactericidal activity in excretory-secretory products, but not somatic extract of adult Nippostrongylus brasiliensis was detected. The bactericidal activity of excretory-secretory products was concentration-dependent, maintained after heat treatment, and preserved after repeated freezing and thawing.Conclusion. The results of this study demonstrate that helminths such as Nippostrongylus brasiliensis release molecules via their excretory-secretory pathway that have broad-spectrum bactericidal activity. The mechanisms responsible for this bactericidal activity remain to be determined and further studies aimed at isolating and identifying active bactericidal molecules are needed
The HST Survey of BL Lacertae Objects. II. Host Galaxies
We have used the HST WFPC2 camera to survey 132 BL Lac objects comprising
seven complete radio-, X-ray-, and optically-selected samples. We obtained
useful images for 110 targets spanning the redshift range 0 < z < 1.3. In two
thirds of the BL Lac images, host galaxies are detected, including nearly all
for z < 0.5 (58 of 63). The highest redshift host galaxy detected is in a BL
Lac object at z=0.664. In 58 of the 72 resolved host galaxies, a de Vaucouleurs
profile is significantly preferred, at >99% confidence, over a pure exponential
disk; the two fits are comparable in the remaining 14 cases. These results
limit the number of disk systems to at most 8% of BL Lacs (at 99% confidence),
and are consistent with all BL~Lac host galaxies being ellipticals. The
detected host galaxies are luminous ellipticals with a median absolute
K-corrected magnitude of M_R= -23.7 +- 0.6 mag, at least one magnitude brighter
than M* and comparable to brightest cluster galaxies. The galaxy morphologies
are generally smooth and undisturbed, with small or negligible ellipticities
(<0.2). There is no correlation between host galaxy and observed nuclear
magnitude or estimated jet power corrected for beaming. If black hole mass is
correlated linearly with bulge mass in general, this implies a large range in
Eddington ratio. Present data strongly support the unification picture with FR
I galaxies constituting the bulk of the parent population of BL Lac objects.Comment: Accepted for publication on ApJ. 38 pages, 8 figure
HST imaging of CFRS and LDSS galaxies - I: Morphological Properties
(Abridged) We analyse Hubble Space Telescope images of a complete sample of
341 galaxies drawn from both the Canada France and Autofib/Low Dispersion
Survey Spectrograph ground-based redshift surveys. We discuss morphological
classifications of these galaxies, and quantify possible biases that may arise
from various redshift-dependent effects. We then discuss these biases in the
context of automated classifications, and quantify the expected
misclassification in our system. After allowing for such biases, the redshift
distribution for normal spirals, together with their luminosity function
derived as a function of redshift, indicates approximately 1 magnitude of
luminosity evolution in B(AB) by z=1. The elliptical sample is too small for
precise evolutionary constraints. However, we find a substantial increase in
the proportion of galaxies with irregular morphology at large redshift. These
galaxies also appear to be the dominant cause of the rapid rise with redshift
in the blue luminosity density identified in the redshift surveys. Although
galaxies with irregular morphology may well comprise a mixture of different
physical systems and might not correspond to present day irregulars, it is
clear that the apparently declining abundance and luminosities of our distant
``irregulars'' holds an important key to understanding recent evolution in the
star formation history of normal galaxies.Comment: 51 pages (14 PS-figures, 3 figures as GIFs) To be published in in Ap
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