1,707 research outputs found
Measuring Sizes of Marginally Resolved Young Globular Clusters with HST
We present a method to derive sizes of marginally resolved star clusters from
HST/WFPC2 observations by fitting King models to observations. We describe
results on both simulated images and on observations of young compact clusters
in NGC 3597 and NGC 1275. From the simulations, we find that we can measure
King model concentrations (c) to an accuracy of about a factor of two for all
combinations of c and King radius (r_0) of interest if the data have high S/N
(>~ 500 for the integrated brightness). If the concentration is accurately
measured, we can measure the King radius accurately. For lower S/N, marginally
resolved King profiles suffer from a degeneracy; different values of the
concentration give different r_0 but have comparable reduced chi-squared
values. In this case, neither the core radius nor the concentration can be
constrained individually, but the half-light radius can be recovered
accurately.
In NGC 3597, we can only differentiate between concentrations for the very
brightest clusters; these suggest a concentration of ~ 2. Assuming a
concentration of 2 for the rest of the objects, we find an average King radius
for the clusters in NGC 3597 of 0.7 pc, while the clusters in NGC 1275 have an
average radius of 1.1 pc. These are similar to the average core radii for
Galactic globular clusters, 0.92 pc. We find average half-light radii of 5.4 pc
and 6.2 pc for the young clusters in NGC 3597 and NGC 1275, respectively, while
the average half-light radii of Galactic globulars is 3.4 pc. The spread in the
derived radial parameters in each cluster system is comparable to that observed
in the Galactic globular cluster system.Comment: 38 pages, 19 figures, accepted for publication in PAS
Targeting tauopathy with engineered tau-degrading intrabodies
BACKGROUND: The accumulation of pathological tau is the main component of neurofibrillary tangles and other tau aggregates in several neurodegenerative diseases, referred to as tauopathies. Recently, immunotherapeutic approaches targeting tau have been demonstrated to be beneficial in decreasing tauopathy in animal models. We previously found that passive immunotherapy with anti-tau antibody to human tau or expression of an anti-tau secreted single-chain variable fragment (scFv) in the central nervous system of a mouse model of tauopathy decreased but did not remove all tau-associated pathology. Although these and other studies demonstrate that conventional immunotherapeutic approaches targeting tau can influence tau pathogenesis, the majority of pathological tau remains in the cytosol of cells, not typically accessible to an extracellular antibody. Therefore, we reasoned targeting intracellular tau might be more efficacious in preventing or decreasing tauopathy.
METHODS: By utilizing our anti-tau scFv, we generated anti-tau intrabodies for the expression in the cytosol of neurons. To enhance the degradation capacity of conventional intrabodies, we engineered chimeric anti-tau intrabodies fused to ubiquitin harboring distinct mutations that shuttle intracellular tau for either the proteasome or lysosomal mediated degradation. To evaluate the efficacy in delaying or eliminating tauopathy, we expressed our tau degrading intrabodies or controls in human tau transgenic mice by adeno-associated virus prior to overt tau pathology and after tau deposition.
RESULTS: Our results demonstrate, the expression of chimeric anti-tau intrabodies significantly reduce tau protein levels in primary neuronal cultures expression human tau relative to a non-modified anti-tau intrabody. We found the expression of engineered tau-degrading intrabodies destined for proteasomal-mediated degradation are more effective in delaying or eliminating tauopathy than a conventional intrabody in aged human tau transgenic mice.
CONCLUSION: This study, harnesses the strength of intrabodies that are amendable for targeting specific domains or modifications with the cell-intrinsic mechanisms that regulate protein degradation providing a new immunotherapeutic approach with potentially improved efficacy
BiDi screen: a thin, depth-sensing LCD for 3D interaction using light fields
We transform an LCD into a display that supports both 2D multi-touch and unencumbered 3D gestures. Our BiDirectional (BiDi) screen, capable of both image capture and display, is inspired by emerging LCDs that use embedded optical sensors to detect multiple points of contact. Our key contribution is to exploit the spatial light modulation capability of LCDs to allow lensless imaging without interfering with display functionality. We switch between a display mode showing traditional graphics and a capture mode in which the backlight is disabled and the LCD displays a pinhole array or an equivalent tiled-broadband code. A large-format image sensor is placed slightly behind the liquid crystal layer. Together, the image sensor and LCD form a mask-based light field camera, capturing an array of images equivalent to that produced by a camera array spanning the display surface. The recovered multi-view orthographic imagery is used to passively estimate the depth of scene points. Two motivating applications are described: a hybrid touch plus gesture interaction and a light-gun mode for interacting with external light-emitting widgets. We show a working prototype that simulates the image sensor with a camera and diffuser, allowing interaction up to 50 cm in front of a modified 20.1 inch LCD.National Science Foundation (U.S.) (Grant CCF-0729126)Alfred P. Sloan Foundatio
The Unusual Spectral Energy Distribution of a Galaxy Previously Reported to be at Redshift 6.68
Observations of distant galaxies are important both for understanding how
galaxies form and for probing the physical conditions of the universe at the
earliest epochs. It is, however, extremely difficult to identify galaxies at
redshift z>5, because these galaxies are faint and exhibit few spectral
features. In a previous work, we presented observations that supported the
identification of a galaxy at redshift z = 6.68 in a deep STIS field. Here we
present new ground-based photometry of the galaxy. We find that the galaxy
exhibits moderate detections of flux in the optical B and V images that are
inconsistent with the expected absence of flux at wavelength shortward of the
redshifted Lyman-alpha emission line of a galaxy at redshift z>5. In addition,
the new broad-band imaging data not only show flux measurements of this galaxy
that are incompatible with the previous STIS measurement, but also suggest a
peculiar spectral energy distribution that cannot be fit with any galaxy
spectral template at any redshift. We therefore conclude that the redshift
identification of this galaxy remains undetermined.Comment: 9 pages, 2 figures; To appear in Nature (30 November 2000
Monitoring and modeling infiltration–recharge dynamics of managed aquifer recharge with desalinated seawater
We study the relation between surface infiltration and groundwater
recharge during managed aquifer recharge (MAR) with desalinated seawater in
an infiltration pond, at the Menashe site that overlies the northern part of
the Israeli Coastal Aquifer. We monitor infiltration dynamics at multiple
scales (up to the scale of the entire pond) by measuring the ponding depth,
sediment water content and groundwater levels, using pressure sensors,
single-ring infiltrometers, soil sensors, and observation wells. During a
month (January 2015) of continuous intensive MAR
(2.45  ×  10<sup>6</sup> m<sup>3</sup> discharged to a 10.7 ha area),
groundwater level has risen by 17 m attaining full connection with the pond,
while average infiltration rates declined by almost 2 orders of magnitude
(from  ∼  11 to  ∼  0.4 m d<sup>−1</sup>). This reduction can be
explained solely by the lithology of the unsaturated zone that includes
relatively low-permeability sediments. Clogging processes at the pond-surface
– abundant in many MAR operations – are negated by the high-quality
desalinated seawater (turbidity  ∼  0.2 NTU, total dissolved solids
 ∼  120 mg L<sup>−1</sup>) or negligible compared to the low-permeability
layers. Recharge during infiltration was estimated reasonably well by simple
analytical models, whereas a numerical model was used for estimating
groundwater recharge after the end of infiltration. It was found that a
calibrated numerical model with a one-dimensional representative sediment
profile is able to capture MAR dynamics, including temporal reduction of
infiltration rates, drainage and groundwater recharge. Measured infiltration
rates of an independent MAR event (January 2016) fitted well to those
calculated by the calibrated numerical model, showing the model validity. The
successful quantification methodologies of the temporal groundwater recharge
are useful for MAR practitioners and can serve as an input for groundwater
flow models
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