1,039 research outputs found
Anterior Chamber Angle Evaluation Using Gonioscopy: Consistency and Agreement between Optometrists and Ophthalmologists
SIGNIFICANCE In our intermediate-tier glaucoma care clinic, we demonstrate fair to moderate agreement in gonioscopy examination between optometrists and ophthalmologists, but excellent agreement when considering open versus closed angles. We highlight the need for increased consistency in the evaluation and recording of angle status using gonioscopy. PURPOSE The consistency of gonioscopy results obtained by different clinicians is not known but is important in moving toward practice modalities such as telemedicine and collaborative care clinics. The purpose of this study was to evaluate the description and concordance of gonioscopy results among different practitioners. METHODS The medical records of 101 patients seen within a collaborative care glaucoma clinic who had undergone gonioscopic assessment by two clinicians (one optometrist and either one general ophthalmologist [n = 50] or one glaucoma specialist [n = 51]) were reviewed. The gonioscopy records were evaluated for their descriptions of deepest structure seen, trabecular pigmentation, iris configuration, and other features. These were compared between clinicians (optometrist vs. ophthalmologist) and against the final diagnosis. RESULTS Overall, 51.9 and 59.8% of angles were graded identically in terms of deepest visible structure when comparing between optometrist versus general ophthalmologist and optometrist versus glaucoma specialist, respectively. The concordance increased when considering ±1 of the grade (67.4 and 78.5%, respectively), and agreement with the final diagnosis was high (>90%). Variations in angle grading other than naming structures were observed (2.0, 30, and 3.9% for optometrist, general ophthalmologist, and glaucoma specialist, respectively). Most of the time, trabecular pigmentation or iris configuration was not described. CONCLUSIONS Fair to moderate concordance in gonioscopy was achieved between optometrists and ophthalmologists in a collaborative care clinic in which there is consistent feedback and clinical review. To move toward unified medical records and a telemedicine model, improved consistency of record keeping and angle description is required
Variation in Grazing Sward Chicory Content After Periods of Low Rainfall
Multispecies (MS) swards can reduce chemical nitrogen (N) fertiliser requirement due to the legume components of the sward mixtures, and have the potential to increase drought tolerance, particularly where chicory (CH, Chicorium intybus L.) is included in the sward mixture. A grazed plot experiment was established to investigate the persistency of forage herb species in MS swards under typical Irish grazing conditions. The swards contained three plant functional groups: grass, legume and herb; four sward types were established which included sward mixtures of the following species: perennial ryegrass (PRG, Lolium perenne L.) white clover (WC, Trifolium repens L.), red clover (RC, Trifolium pratense L.), CH and ribwort plantain (PL, Plantago lanceolata L.). The sward content of the various species in the sown mixtures was evaluated over three years (2020, 2021 and 2022). The summer of 2022 experienced dry weather conditions in which rainfall was well below average thus providing an opportunity to assess the drought tolerance of CH in grazed swards. The proportion of sward CH content from two late season cuts was assessed over the three years and this study reports the changes in sward CH content between years and grazing rotations. Average sward CH content was 14.7, 6.1, and 1.5% across all sward types in late summer of 2020, 2021 and 2022, respectively; average sward CH content was 13.7, 9.4 and 24.6 across all sward types in autumn of 2020, 2021 and 2022, respectively
Early Attachment Disruption, Inflammation, and Vulnerability for Depression in Rodent and Primate Models
Early experiments in nonhuman primates established the relation between disruption of filial attachment and depressive-like outcomes. Subsequent studies in rats and mice have been instrumental in linking depressive-like outcomes to disturbances in maternal behavior. Another aspect of attachment disruption, absence of the attachment object per se, may be studied more effectively in a different laboratory rodent—the guinea pig. Here, we discuss the rationale for using guinea pigs for this work. We then review guinea pig studies providing evidence for inflammatory mechanisms mediating both depressive-like behavior during separation as well as sensitization of stress responsiveness such as is thought to lead to increased vulnerability to depression at later ages. Finally, we discuss recent complementary work in adult monkeys that suggests cross-species generalizability of broad principles derived from the guinea pig experiments. Overall, the findings provide experimental support for human research implicating inflammatory mechanisms in the development of increased stress responsiveness and vulnerability to depression following attachment disruption and other forms of early-life stress. Specifically, the findings suggest inflammatory mechanisms may set in motion a cascade of underlying processes that mediate later increased stress responsiveness and, therefore, depression susceptibility
Photometric redshifts from reconstructed QSO templates
From SDSS commissioning photometric and spectroscopic data, we investigate
the utility of photometric redshift techniques to the task of estimating QSO
redshifts. We consider empirical methods (e.g. nearest-neighbor searches and
polynomial fitting), standard spectral template fitting and hybrid approaches
(i.e. training spectral templates from spectroscopic and photometric
observations of QSOs). We find that in all cases, due to the presence of strong
emission-lines within the QSO spectra, the nearest-neighbor and template
fitting methods are superior to the polynomial fitting approach. Applying a
novel reconstruction technique, we can, from the SDSS multicolor photometry,
reconstruct a statistical representation of the underlying SEDs of the SDSS
QSOs. Although, the reconstructed templates are based on only broadband
photometry the common emission lines present within the QSO spectra can be
recovered in the resulting spectral energy distributions. The technique should
be useful in searching for spectral differences among QSOs at a given redshift,
in searching for spectral evolution of QSOs, in comparing photometric redshifts
for objects beyond the SDSS spectroscopic sample with those in the well
calibrated photometric redshifts for objects brighter than 20th magnitude and
in searching for systematic and time variable effects in the SDSS broad band
photometric and spectral photometric calibrations.Comment: 21 pages, 9 figures, LaTeX AASTeX, submitted to A
Photometric Redshifts of Quasars
We demonstrate that the design of the Sloan Digital Sky Survey (SDSS) filter
system and the quality of the SDSS imaging data are sufficient for determining
accurate and precise photometric redshifts (``photo-z''s) of quasars. Using a
sample of 2625 quasars, we show that photo-z determination is even possible for
z<=2.2 despite the lack of a strong continuum break that robust photo-z
techniques normally require. We find that, using our empirical method on our
sample of objects known to be quasars, approximately 70% of the photometric
redshifts are correct to within delta z = 0.2; the fraction of correct
photometric redshifts is even better for z>3. The accuracy of quasar
photometric redshifts does not appear to be dependent upon magnitude to nearly
21st magnitude in i'. Careful calibration of the color-redshift relation to
21st magnitude may allow for the discovery of on the order of 10^6 quasars
candidates in addition to the 10^5 quasars that the SDSS will confirm
spectroscopically. We discuss the efficient selection of quasar candidates from
imaging data for use with the photometric redshift technique and the potential
scientific uses of a large sample of quasar candidates with photometric
redshifts.Comment: 29 pages, 8 figures, submitted to A
High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data IV: Luminosity Function from the Fall Equatorial Stripe Sampl
This is the fourth paper in a series aimed at finding high-redshift quasars
from five-color imaging data taken along the Celestial Equator by the SDSS.
during its commissioning phase. In this paper, we use the color-selected sample
of 39 luminous high-redshift quasars presented in Paper III to derive the
evolution of the quasar luminosity function over the range of 3.6<z<5.0, and
-27.5<M_1450<-25.5 (Omega=1, H_0=50 km s^-1 Mpc^-1). We use the selection
function derived in Paper III to correct for sample incompleteness. The
luminosity function is estimated using three different methods: (1) the 1/V_a
estimator; (2) a maximum likelihood solution, assuming that the density of
quasars depends exponentially on redshift and as a power law in luminosity and
(3) Lynden-Bell's non-parametric C^- estimator. All three methods give
consistent results. The luminous quasar density decreases by a factor of ~ 6
from z=3.5 to z=5.0, consistent with the decline seen from several previous
optical surveys at z<4.5. The luminosity function follows psi(L) ~ L^{-2.5} for
z~4 at the bright end, significantly flatter than the bright end luminosity
function psi(L) \propto L^{-3.5} found in previous studies for z<3, suggesting
that the shape of the quasar luminosity function evolves with redshift as well,
and that the quasar evolution from z=2 to 5 cannot be described as pure
luminosity evolution. Possible selection biases and the effect of dust
extinction on the redshift evolution of the quasar density are also discussed.Comment: AJ accepted, with minor change
Weak Lensing with SDSS Commissioning Data: The Galaxy-Mass Correlation Function To 1/h Mpc
(abridged) We present measurements of galaxy-galaxy lensing from early
commissioning imaging data from the Sloan Digital Sky Survey (SDSS). We measure
a mean tangential shear around a stacked sample of foreground galaxies in three
bandpasses out to angular radii of 600'', detecting the shear signal at very
high statistical significance. The shear profile is well described by a
power-law. A variety of rigorous tests demonstrate the reality of the
gravitational lensing signal and confirm the uncertainty estimates. We
interpret our results by modeling the mass distributions of the foreground
galaxies as approximately isothermal spheres characterized by a velocity
dispersion and a truncation radius. The velocity dispersion is constrained to
be 150-190 km/s at 95% confidence (145-195 km/s including systematic
uncertainties), consistent with previous determinations but with smaller error
bars. Our detection of shear at large angular radii sets a 95% confidence lower
limit , corresponding to a physical radius of
kpc, implying that galaxy halos extend to very large radii. However, it is
likely that this is being biased high by diffuse matter in the halos of groups
and clusters. We also present a preliminary determination of the galaxy-mass
correlation function finding a correlation length similar to the galaxy
autocorrelation function and consistency with a low matter density universe
with modest bias. The full SDSS will cover an area 44 times larger and provide
spectroscopic redshifts for the foreground galaxies, making it possible to
greatly improve the precision of these constraints, measure additional
parameters such as halo shape, and measure the properties of dark matter halos
separately for many different classes of galaxies.Comment: 28 pages, 11 figures, submitted to A
High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data II: The Spring Equatorial Stripe
This is the second paper in a series aimed at finding high-redshift quasars
from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by
the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this
paper, we present 22 high-redshift quasars (z>3.6) discovered from ~250 deg^2
of data in the spring Equatorial Stripe, plus photometry for two previously
known high-redshift quasars in the same region of sky. Our success rate of
identifying high-redshift quasars is 68%. Five of the newly discovered quasars
have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92 and 5.03). All the
quasars have i* < 20.2 with absolute magnitude -28.8 < M_B < -26.1 (h=0.5,
q_0=0.5). Several of the quasars show unusual emission and absorption features
in their spectra, including an object at z=4.62 without detectable emission
lines, and a Broad Absorption Line (BAL) quasar at z=4.92.Comment: 28 pages, AJ in press (Jan 2000), final version with minor changes;
high resolution finding charts available at
http://www.astro.princeton.edu/~fan/paper/qso2.htm
Optical and Radio Properties of Extragalactic Sources Observed by the FIRST and SDSS Surveys
We discuss the optical and radio properties of 30,000 FIRST sources
positionally associated with an SDSS source in 1230 deg of sky. The
majority (83%) of the FIRST sources identified with an SDSS source brighter
than r=21 are optically resolved. We estimate an upper limit of 5% for the
fraction of quasars with broad-band optical colors indistinguishable from those
of stars. The distribution of quasars in the radio flux -- optical flux plane
supports the existence of the "quasar radio-dichotomy"; 8% of all quasars with
i<18.5 are radio-loud and this fraction seems independent of redshift and
optical luminosity. The radio-loud quasars have a redder median color by 0.08
mag, and a 3 times larger fraction of objects with red colors. FIRST galaxies
represent 5% of all SDSS galaxies with r<17.5, and 1% for r<20, and are
dominated by red galaxies. Magnitude and redshift limited samples show that
radio galaxies have a different optical luminosity distribution than non-radio
galaxies selected by the same criteria; when galaxies are further separated by
their colors, this result remains valid for both blue and red galaxies. The
distributions of radio-to-optical flux ratio are similar for blue and red
galaxies in redshift-limited samples; this similarity implies that the
difference in their luminosity functions, and resulting selection effects, are
the dominant cause for the preponderance of red radio galaxies in flux-limited
samples. We confirm that the AGN-to-starburst galaxy number ratio increases
with radio flux, and find that radio emission from AGNs is more concentrated
than radio emission from starburst galaxies (abridged).Comment: submitted to AJ, color gif figures, PS figures available from
[email protected]
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