1,275 research outputs found
Linguistic Development of Children and the Syntax of Basals
Children\u27s ability to reflect upon language begins to appear about age two (Clark, 1978). During the early stages of language development, children correct their own pronunciations, question the appropriateness of speech styles, play with different linguistic units, and make judgments concerning language usage for varying situations (Clark, 1978). Children exhibit an increasing awareness of language with age and soon become aware of both the form and function of language. Their metacognitive skills become apparent as they progress from the simple to the more complex linguistic structures. Children\u27s language acquisition and cognitive development continue to develop during the early years of school (Clark, 1978)
The classification and structure of megafaunal assemblages in the Venezuela Basin, Caribbean Sea
Data from 23 benthic trawls collected from the Venezuela Basin (3411–5062 m water depth) indicate that megafauna are less abundant than in basins of similar depths in the Atlantic and are segregated by sedimentary province. Taxonomic assemblages, in terms of abundance and biomass, from three sites coincide with distinctions of sedimentary characteristics among the pelagic, hemipelagic and turbidite sedimentary provinces. Mollusks, decapods and fishes are most abundant in trawls collected from the pelagic and hemipelagic provinces and anemones and holothurians are most abundant in trawls collected from the turbidite province. Sponges dominate the biomass of fauna in trawls collected in the turbidite and hemipelagic provinces and fishes dominate the biomass of trawls collected in the pelagic province. Several biological and physical aspects of the basin contribute to the segregation of the megafauna into distinct communities. Sponges and anthropogenic debris (coal, coal clinker and tar balls) reaching the sea floor create a habitat that is exploited by sessile suspension feeders requiring a hard substrate. Filter-feeding anemones attached to debris occur in such abundance that it elevates the importance of suspension feeders and depresses species diversity at the turbidite site. Biomass and average size of megafaunal deposit feeders in the basin decrease with decreasing amounts of organic carbon and nitrogen content of the sediment. Distribution and composition of filter-feeding megafaunal biomass in the Venezuela Basin are explained largely by proximity to sources of organic matter. Detrital carbonate may also play a role in controlling distribution and density of megafauna by diluting food resources in the sediments
Detection of Crab Giant Pulses Using the Mileura Widefield Array Low Frequency Demonstrator Field Prototype System
We report on the detection of giant pulses from the Crab Nebula pulsar at a
frequency of 200 MHz using the field deployment system designed for the Mileura
Widefield Array's Low Frequency Demonstrator (MWA-LFD). Our observations are
among the first high-quality detections at such low frequencies. The measured
pulse shapes are deconvolved for interstellar pulse broadening, yielding a
pulse-broadening time of 670100 s, and the implied strength of
scattering (scattering measure) is the lowest that is estimated towards the
Crab nebula from observations made so far. The sensitivity of the system is
largely dictated by the sky background, and our simple equipment is capable of
detecting pulses that are brighter than 9 kJy in amplitude. The brightest
giant pulse detected in our data has a peak amplitude of 50 kJy, and the
implied brightness temperature is K. We discuss the giant pulse
detection prospects with the full MWA-LFD system. With a sensitivity over two
orders of magnitude larger than the prototype equipment, the full system will
be capable of detecting such bright giant pulses out to a wide range of
Galactic distances; from 8 to 30 kpc depending on the frequency.
The MWA-LFD will thus be a highly promising instrument for the studies of giant
pulses and other fast radio transients at low frequencies.Comment: 10 pages, 6 figures, Accepted for publication in the Astrophysical
Journa
BATSE Observations of Gamma-Ray Burst Spectra. IV. Time-Resolved High-Energy Spectroscopy
We report on the temporal behavior of the high-energy power law continuum
component of gamma-ray burst spectra with data obtained by the Burst and
Transient Source Experiment. We have selected 126 high fluence and high flux
bursts from the beginning of the mission up until the present. Much of the data
were obtained with the Large Area Detectors, which have nearly all-sky
coverage, excellent sensitivity over two decades of energy and moderate energy
resolution, ideal for continuum spectra studies of a large sample of bursts at
high time resolution. At least 8 spectra from each burst were fitted with a
spectral form that consisted of a low-energy power law, a spectral break at
middle energies and a high-energy continuum. In most bursts (122), the
high-energy continuum was consistent with a power law. The evolution of the
fitted high-energy power-law index over the selected spectra for each burst is
inconsistent with a constant for 34% of the total sample. The sample
distribution of the average value for the index from each burst is fairly
narrow, centered on -2.12. A linear trend in time is ruled out for only 20% of
the bursts, with hard-to-soft evolution dominating the sample (100 events). The
distribution for the total change in the power-law index over the duration of a
burst peaks at the value -0.37, and is characterized by a median absolute
deviation of 0.39, arguing that a single physical process is involved. We
present analyses of the correlation of the power-law index with time, burst
intensity and low-energy time evolution. In general, we confirm the general
hard-to-soft spectral evolution observed in the low-energy component of the
continuum, while presenting evidence that this evolution is different in nature
from that of the rest of the continuum.Comment: 30 pages, with 2 tables and 9 figures To appear in The Astrophysical
Journal, April 1, 199
Towards a fullerene-based quantum computer
Molecular structures appear to be natural candidates for a quantum
technology: individual atoms can support quantum superpositions for long
periods, and such atoms can in principle be embedded in a permanent molecular
scaffolding to form an array. This would be true nanotechnology, with
dimensions of order of a nanometre. However, the challenges of realising such a
vision are immense. One must identify a suitable elementary unit and
demonstrate its merits for qubit storage and manipulation, including input /
output. These units must then be formed into large arrays corresponding to an
functional quantum architecture, including a mechanism for gate operations.
Here we report our efforts, both experimental and theoretical, to create such a
technology based on endohedral fullerenes or 'buckyballs'. We describe our
successes with respect to these criteria, along with the obstacles we are
currently facing and the questions that remain to be addressed.Comment: 20 pages, 13 figs, single column forma
Scaling and singularities in the entrainment of globally-coupled oscillators
The onset of collective behavior in a population of globally coupled
oscillators with randomly distributed frequencies is studied for phase
dynamical models with arbitrary coupling. The population is described by a
Fokker-Planck equation for the distribution of phases which includes the
diffusive effect of noise in the oscillator frequencies. The bifurcation from
the phase-incoherent state is analyzed using amplitude equations for the
unstable modes with particular attention to the dependence of the nonlinearly
saturated mode on the linear growth rate . In general
we find where is the
diffusion coefficient and is the mode number of the unstable mode. The
unusual factor arises from a singularity in the cubic term of
the amplitude equation.Comment: 11 pages (Revtex); paper submitted to Phys. Rev. Let
Benefits of robotic cystectomy with intracorporeal diversion for patients with low cardiorespiratory fitness: a prospective cohort study
Background:
Patients undergoing radical cystectomy have associated comorbidities resulting in reduced cardiorespiratory fitness. Preoperative cardiopulmonary exercise testing (CPET) measures including anaerobic threshold (AT) can predict major adverse events (MAE) and hospital length of stay (LOS) for patients undergoing open and robotic cystectomy with extracorporeal diversion. Our objective was to determine the relationship between CPET measures and outcome in patients undergoing robotic radical cystectomy and intracorporeal diversion (intracorporeal robotic assisted radical cystectomy [iRARC]).
Methods:
A single institution prospective cohort study in patients undergoing iRARC for muscle invasive and high-grade bladder cancer. Inclusion: patients undergoing standardised CPET before iRARC. Exclusions: patients not consenting to data collection. Data on CPET measures (AT, ventilatory equivalent for carbon dioxide [VE/VCO2] at AT, peak oxygen uptake [VO2]), and patient demographics prospectively collected. Outcome measurements included hospital LOS; 30-day MAE and 90-day mortality data, which were prospectively recorded. Descriptive and regression analyses were used to assess whether CPET measures were associated with or predicted outcomes.
Results:
From June 2011 to March 2015, 128 patients underwent radical cystectomy (open cystectomy, n = 17; iRARC, n = 111). A total of 82 patients who underwent iRARC and CPET and consented to participation were included. Median (interquartile range): age = 65 (58–73); body mass index = 27 (23–30); AT = 10.0 (9–11), Peak VO2 = 15.0 (13–18.5), VE/VCO2 (AT) = 33.0 (30–38). 30-day MAE = 14/111 (12.6%): death = 2, multiorgan failure = 2, abscess = 2, gastrointestinal = 2, renal = 6; 90-day mortality = 3/111 (2.7%). AT, peak VO2, and VE/VCO2 (at AT) were not significant predictors of 30-day MAE or LOS. The results are limited by the absence of control group undergoing open surgery.
Conclusions:
Poor cardiorespiratory fitness does not predict increased hospital LOS or MAEs in patients undergoing iRARC. Overall, MAE and LOS comparable with other series
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