We report the detection of an ultra-bright fast radio burst (FRB) from a modest, 3.4-day pilot survey with the Australian Square Kilometre Array Pathfinder. The survey was conducted in a wide-field ...fly's-eye configuration using the phased-array-feed technology deployed on the array to instantaneously observe an effective area of 160 deg2, and achieve an exposure totaling 13200 deg2 hr . We constrain the position of FRB 170107 to a region in size (90% containment) and its fluence to be 58 6 Jy ms. The spectrum of the burst shows a sharp cutoff above 1400 MHz, which could be due to either scintillation or an intrinsic feature of the burst. This confirms the existence of an ultra-bright ( Jy ms) population of FRBs.
The Australia SKA Pathfinder (ASKAP) is a new telescope under development as a world-class high-dynamic-range wide-field-of-view survey instrument. It will utilize focal plane phased array feeds on ...the 36 12-m antennas that will compose the array. The large amounts of data present a huge computing challenge, and ASKAP will store data products in an archive after near real-time pipeline processing. This powerful instrument will be deployed at a new radio-quiet observatory, the Murchison Radio-astronomy Observatory in the midwest region of Western Australia, to enable sensitive surveys of the entire sky to address some of the big questions in contemporary physics. As a pathfinder for the SKA, ASKAP will demonstrate field of view enhancement and computing/processing technology as well as the operation of a large-scale radio array in a remote and radio-quiet region of Australia.
The deleterious effects of prolonged sleep deprivation on behavior and cognition are a concern in modern society. Persons at risk for impaired performance and health-related issues resulting from ...prolonged sleep loss would benefit from agents capable of reducing these detrimental effects at the time they are sleep deprived. Agents capable of improving cognition by enhancing brain activity under normal circumstances may also have the potential to reduce the harmful or unwanted effects of sleep deprivation. The significant prevalence of excitatory alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamatergic receptors in the brain provides a basis for implementing a class of drugs that could act to alter or remove the effects of sleep deprivation. The ampakine CX717 (Cortex Pharmaceuticals), a positive allosteric modulator of AMPA receptors, was tested for its ability to enhance performance of a cognitive, delayed match-to-sample task under normal circumstances in well-trained monkeys, as well as alleviate the detrimental effects of 30-36 h of sleep deprivation. CX717 produced a dose-dependent enhancement of task performance under normal alert testing conditions. Concomitant measures of regional cerebral metabolic rates for glucose (CMRglc) during the task, utilizing positron emission tomography, revealed increased activity in prefrontal cortex, dorsal striatum, and medial temporal lobe (including hippocampus) that was significantly enhanced over normal alert conditions following administration of CX717. A single night of sleep deprivation produced severe impairments in performance in the same monkeys, accompanied by significant alterations in task-related CMRglc in these same brain regions. However, CX717 administered to sleep-deprived monkeys produced a striking removal of the behavioral impairment and returned performance to above-normal levels even though animals were sleep deprived. Consistent with this recovery, CMRglc in all but one brain region affected by sleep deprivation was also returned to the normal alert pattern by the drug. The ampakine CX717, in addition to enhancing cognitive performance under normal alert conditions, also proved effective in alleviating impairment of performance due to sleep deprivation. Therefore, the ability to activate specific brain regions under normal alert conditions and alter the deleterious effects of sleep deprivation on activity in those same regions indicate a potential role for ampakines in sustaining performance under these types of adverse conditions.
Several next-generation radio telescopes, now in the planning stages, are based on phased-array technology. One reason for this is to make use of adaptive nulling techniques to combat radio frequency ...interference, which is a growing problem for radio astronomy. This paper presents a low-complexity approach to interference nulling which is suitable for use in such systems. The approach uses subspace-tracking to identify interference, followed by spatial projections to place deep nulls in the directions of interferers. This technique overcomes two limitations of power-minimization algorithms (e.g., "minimum variance"), namely power inversion and pattern rumble, which create serious problems for radio astronomy. Furthermore, this technique imposes a lower computational burden and provides side information which is useful in later stages of data processing. Performance results from a phased array demonstrator system and a simulation are presented.
Rationale
Performance of cognitive tasks in nonhuman primates (NHPs) requires specific brain regions to make decisions under different degrees of difficulty or “cognitive load.”
Objective
Local ...cerebral metabolic activity (
18
FFDG PET imaging) in dorsolateral prefrontal cortex (DLPFC), medial temporal lobe (MTL), and dorsal striatum (DStr) is examined in NHPs performing a delayed-match-to-sample (DMS) task with variable degrees of cognitive load.
Materials and methods
Correlations between cognitive load and degree of brain metabolic activity were obtained with respect to the influence of the ampakine CX717 (Cortex Pharmaceuticals), using brain imaging and recordings of neuronal activity in NHPs and measures of intracellular calcium release in rat hippocampal slices.
Results
Activation of DLPFC, MTL, and DStr reflected changes in performance related to cognitive load within the DMS task and were engaged primarily on high load trials. Similar increased activation patterns and improved performance were also observed following administration of CX717. Sleep deprivation in NHPs produced impaired performance and reductions in brain activation which was reversed by CX717. One potential basis for this facilitation of cognition by CX717 was increased firing of task-specific hippocampal cells. Synaptic mechanisms affected by CX717 were examined in rat hippocampal slices which showed that
N
-methyl-
d
-aspartic acid-mediated release of intracellular calcium was reduced in slices from sleep-deprived rats and reversed by application of CX717 to the bathing medium.
Conclusions
The findings provide insight into how cognition is enhanced by CX717 in terms of brain, and underlying neural, processes that are activated on high vs. low cognitive load trials.
Maintenance of cognitive control is a major concern for many human disease conditions; therefore, a major goal of human neuroprosthetics is to facilitate and/or recover the cognitive function when ...such circumstances impair appropriate decision making.
Minicolumnar activity from the prefrontal cortex (PFC) was recorded from nonhuman primates trained to perform a delayed match to sample (DMS), via custom-designed conformal multielectrode arrays that provided inter-laminar recordings from neurons in the PFC layer 2/3 and layer 5. Such recordings were analyzed via a previously demonstrated nonlinear multi-input-multi-output (MIMO) neuroprosthesis in rodents, which extracted and characterized multicolumnar firing patterns during DMS performance.
The MIMO model verified that the conformal recorded individual PFC minicolumns responded to entrained target selections in patterns critical for successful DMS performance. This allowed the substitution of task-related layer 5 neuron firing patterns with electrical stimulation in the same recording regions during columnar transmission from layer 2/3 at the time of target selection. Such stimulation improved normal task performance, but more importantly, recovered performance when applied as a neuroprosthesis following the pharmacological disruption of decision making in the same task.
These findings provide the first successful application of neuroprosthesis in the primate brain designed specifically to restore or repair the disrupted cognitive function.
ASKAP H i imaging of the galaxy group IC 1459 Serra, P; Koribalski, B; Kilborn, V ...
Monthly notices of the Royal Astronomical Society,
09/2015, Letnik:
452, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present H i imaging of the galaxy group IC 1459 carried out with six antennas of the Australian Square Kilometre Array Pathfinder equipped with phased-array feeds. We detect and resolve H i in 11 ...galaxies down to a column density of ∼1020 cm−2 inside a ∼6 deg2 field and with a resolution of ∼1 arcmin on the sky and ∼8 km s−1 in velocity. We present H i images, velocity fields and integrated spectra of all detections, and highlight the discovery of three H i clouds – two in the proximity of the galaxy IC 5270 and one close to NGC 7418. Each cloud has an H i mass of ∼109 M⊙ and accounts for ∼15 per cent of the H i associated with its host galaxy. Available images at ultraviolet, optical and infrared wavelengths do not reveal any clear stellar counterpart of any of the clouds, suggesting that they are not gas-rich dwarf neighbours of IC 5270 and NGC 7418. Using Parkes data, we find evidence of additional extended, low-column-density H i emission around IC 5270, indicating that the clouds are the tip of the iceberg of a larger system of gas surrounding this galaxy. This result adds to the body of evidence on the presence of intragroup gas within the IC 1459 group. Altogether, the H i found outside galaxies in this group amounts to several times 109 M⊙, at least 10 per cent of the H i contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution.
PDF
