6,561 research outputs found
Common visual problems in children with disability
Children with disability are at a substantially higher risk of visual impairment (VI) (10.5% compared with 0.16%) but also of ocular disorders of all types, including refractive errors and strabismus. The aetiology of VI in children with disability reflects that of the general population and includes cerebral VI, optic atrophy, as well as primary visual disorders such as retinal dystrophies and structural eye anomalies. VI and other potentially correctable ocular disorders may not be recognised without careful assessment and are frequently unidentified in children with complex needs. Although assessment may be more challenging than in other children, identifying these potential additional barriers to learning and development may be critical. There is a need to develop clearer guidelines, referral pathways and closer working between all professionals involved in the care of children with disability and visual disorders to improve our focus on the assessment of vision and outcomes for children with disability
Development and collapse of an Oscillatoria bloom in Loch Leven during July 1994
During 1994, weekly spot-sampling of open water sites on Loch Leven took place from 16th March onwards. Very little difference between spot-sampling sites was observed from 16th March to 5th July. Throughout April and May there was a slow increase in levels of chlorophyll-a, followed by a rapid increase through June, reaching a maximum of 230 micrograms per litre. On 8th July there was a very rapid rise in water temperature, with a corresponding increase in dissolved oxygen and pH. At 0915 hours on 9th July there was a drop in all three variables. These changes were coincident with a marked reduction in chlorophyll-a values falling to 70 micrograms per litre on 12th July. On 16th July evidence of a resurgence of photosynthesis was observed
Low Temperature Scanning Electron Microscopy: Advantages and Applications
Cryo-preparation of specimens for scanning electron microscopy can be completed within a few minutes. Chemical fixation and contact with solvents is avoided, levels of specimen hydration are maintained, low melting-point materials are stabilized, volume changes are minimized and internal structure can be revealed by freeze-fracture. Elements are not lost or substantially relocated prior to X-ray microanalysis and specimen luminescence is enhanced. The displacement of internal structure and material subject to X-ray microanalysis by the growth of ice crystals in hydrated samples can be minimized by adopting fast freezing methods designed to limit ice crystal growth. The technique enables a wide range of industrial and biological materials to be examined rapidly and free from artifacts commonly associated with more conventional preparation methods
Stellar Velocity Dispersion and Black Hole Mass in the Blazar Markarian 501
The recently discovered correlation between black hole mass and stellar
velocity dispersion provides a new method to determine the masses of black
holes in active galaxies. We have obtained optical spectra of Markarian 501, a
nearby gamma-ray blazar with emission extending to TeV energies. The stellar
velocity dispersion of the host galaxy, measured from the calcium triplet lines
in a 2"x3.7" aperture, is 372 +/- 18 km/s. If Mrk 501 follows the M-sigma
correlation defined for local galaxies, then its central black hole has a mass
of (0.9-3.4)x10^9 solar masses. This is significantly larger than some previous
estimates for the central mass in Mrk 501 that have been based on models for
its nonthermal emission. The host galaxy luminosity implies a black hole of
6x10^8 solar masses, but this is not in severe conflict with the mass derived
from the M-sigma relation because the M_BH-L_bulge correlation has a large
intrinsic scatter. Using the emission-line luminosity to estimate the
bolometric luminosity of the central engine, we find that Mrk 501 radiates at
an extremely sub-Eddington level of L/L_Edd ~ 10^-4. Further applications of
the M-sigma relation to radio-loud active galactic nuclei may be useful for
interpreting unified models and understanding the relationship between radio
galaxies and BL Lac objects.Comment: To appear in ApJ Letters. 5 pages, 2 figure
Interferometric Evidence for Resolved Warm Dust in the DQ Tau System
We report on near-infrared (IR) interferometric observations of the
double-lined pre-main sequence (PMS) binary system DQ Tau. We model these data
with a visual orbit for DQ Tau supported by the spectroscopic orbit & analysis
of \citet{Mathieu1997}. Further, DQ Tau exhibits significant near-IR excess;
modeling our data requires inclusion of near-IR light from an 'excess' source.
Remarkably the excess source is resolved in our data, similar in scale to the
binary itself ( 0.2 AU at apastron), rather than the larger circumbinary
disk ( 0.4 AU radius). Our observations support the \citet{Mathieu1997}
and \citet{Carr2001} inference of significant warm material near the DQ Tau
binary.Comment: 14 pgs, 3 figures, ApJL in pres
Baseline tests of the EPC Hummingbird electric passenger vehicle
The rear-mounted internal combustion engine in a four-passenger Volkswagen Thing was replaced with an electric motor made by modifying an aircraft generator and powered by 12 heavy-duty, lead-acid battery modules. Vehicle performance tests were conducted to measure vehicle maximum speed, range at constant speed, range over stop-and-go driving schedules, maximum acceleration, gradeability limit, road energy consumption, road power, indicated energy consumption, braking capability, battery charger efficiency, and battery characteristics. Test results are presented in tables and charts
Variation of Molecular Line Ratios and Cloud Properties in the Arp 299 Galaxy Merger
High resolution observations of 12CO (2.''3), 13CO (3.''9), and HCN (5.''4)
J=1--0 in the galaxy merger Arp 299 (IC 694 and NGC 3690) show the line ratios
vary dramatically across the system. The 12CO/13CO ratio is unusually large, 60
+- 15, at the IC 694 nucleus, where 12CO emission is very strong, and much
smaller, 10 +- 3, in the southern extended disk of that galaxy. Elsewhere, the
12CO/13CO line ratio is 5-20, typical of spiral galaxies. The line ratio
variation in the overlap between the two galaxies is smaller, ranging from 10
+- 3 in the east to 20 +- 4 in the west.
The 12CO/HCN line ratio also varies across Arp 299, although to a lesser
degree. HCN emission is bright towards each galaxy nucleus and in the
extranuclear region of active star formation; it was not detected in the IC 694
disk, or the eastern part of the overlap region, leading to lower limits of 25
and 20 respectively. By contrast, at the nuclei of IC 694 and NGC 3690 the
ratios are 9 +- 1 and 14 +- 3 respectively. In the western part of the overlap
region it is 11 +- 3.Comment: 16 pages, 4 postscript figures, to appear in ApJ Letter
Manufactured analytical solutions for isothermal full-Stokes ice sheet models
We present the detailed construction of a manufactured analytical solution to time-dependent and steady-state isothermal full-Stokes ice sheet problems. The solutions are constructed for two-dimensional flowline and three-dimensional full-Stokes ice sheet models with variable viscosity. The construction is done by choosing for the specified ice surface and bed a velocity distribution that satisfies both mass conservation and the kinematic boundary conditions. Then a compensatory stress term in the conservation of momentum equations and their boundary conditions is calculated to make the chosen velocity distributions as well as the chosen pressure field into exact solutions. By substituting different ice surface and bed geometry formulas into the derived solution formulas, analytical solutions for different geometries can be constructed. <br><br> The boundary conditions can be specified as essential Dirichlet conditions or as periodic boundary conditions. By changing a parameter value, the analytical solutions allow investigation of algorithms for a different range of aspect ratios as well as for different, frozen or sliding, basal conditions. The analytical solutions can also be used to estimate the numerical error of the method in the case when the effects of the boundary conditions are eliminated, that is, when the exact solution values are specified as inflow and outflow boundary conditions
Differentiation of Cardiac from Noncardiac Pleural Effusions in Cats using Second-Generation Quantitative and Point-of-Care NT-proBNP Measurements
BACKGROUND: Pleural effusion is a common cause of dyspnea in cats. Nâterminal proâBâtype natriuretic peptide (NTâproBNP) measurement, using a firstâgeneration quantitative ELISA, in plasma and pleural fluid differentiates cardiac from noncardiac causes of pleural effusion. HYPOTHESIS/OBJECTIVES: To determine whether NTâproBNP measurements using secondâgeneration quantitative ELISA and pointâofâcare (POC) tests in plasma and pleural fluid distinguish cardiac from noncardiac pleural effusions and how results compare to the firstâgeneration ELISA. ANIMALS: Thirtyâeight cats (US cohort) and 40 cats (UK cohort) presenting with cardiogenic or noncardiogenic pleural effusion. METHODS: Prospective cohort study. Twentyâone and 17 cats in the US cohort, and 22 and 18 cats in the UK cohort were classified as having cardiac or noncardiac pleural effusion, respectively. NTâproBNP concentrations in paired plasma and pleural fluid samples were measured using secondâgeneration ELISA and POC assays. RESULTS: The secondâgeneration ELISA differentiated cardiac from noncardiac pleural effusion with good diagnostic accuracy (plasma: sensitivity, 95.2%, specificity, 82.4%; pleural fluid: sensitivity, 100%, specificity, 76.5%). NTâproBNP concentrations were greater in pleural fluid (719 pmol/L (134â1500)) than plasma (678 pmol/L (61â1500), P = 0.003), resulting in different cutâoff values depending on the sample type. The POC test had good sensitivity (95.2%) and specificity (87.5%) when using plasma samples. In pleural fluid samples, the POC test had good sensitivity (100%) but low specificity (64.7%). Diagnostic accuracy was similar between firstâ and secondâgeneration ELISA assays. CONCLUSIONS AND CLINICAL IMPORTANCE: Measurement of NTâproBNP using a quantitative ELISA in plasma and pleural fluid or POC test in plasma, but not pleural fluid, distinguishes cardiac from noncardiac causes of pleural effusion in cats
Evidence for Rotation in the Galaxy at z=3.15 Responsible for a Damped Lyman-alpha Absorption System in the Spectrum of Q2233+1310
Proof of the existence of a significant population of normal disk galaxies at
redshift z>2 would have profound implications for theories of structure
formation and evolution. We present evidence based on Keck HIRES observations
that the damped Lyman-alpha absorber at z=3.15 toward the quasar Q2233+1310 may
well be such an example. Djorgovski et al have recently detected the
Lyman-alpha emission from the absorber, which we assume is at the systemic
redshift of the absorbing galaxy. By examining the profiles of the metal
absorption lines arising from the absorbing galaxy in relation to its systemic
redshift, we find strong kinematical evidence for rotation. Therefore the
absorber is likely to be a disk galaxy. The inferred circular velocity for the
galaxy is >200 km/s. With a separation of ~17 kpc between the galaxy and the
quasar sightline, the implied dynamic mass for the galaxy is >1.6x10(11) solar
mass. The metallicity of the galaxy is found to be [Fe/H]=-1.4, typical of
damped Lyman-alpha galaxies at such redshifts. However, in another damped
galactic rotation is evident. In the latter case, the damped Lyman-alpha
absorber occurs near the background quasar in redshift so its properties may be
influenced by the background quasar. These represent the only two cases at
present for which the technique used here may be applied. Future applications
of the same technique to a large sample of damped Lyman-alpha galaxies may
allow us to determine if a significant population of disk galaxies already
existed only a few billion years after the Big Bang.Comment: AASTEX, 2 PS figures, accepted by ApJ, 6 pages total, replaced on
1-22-97, the only change is the enlarged figure
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