5,346 research outputs found
ELAV mediates 3' UTR extension in the Drosophila nervous system
Post-transcriptional gene regulation is prevalent in the nervous system, where multiple tiers of regulatory complexity contributeto the development and function of highly specialized cell types. Whole-genome studies in Drosophila have identified several hundred genes containing long 3′ extensions in neural tissues. We show that ELAV (embryonic-lethalabnormal visual system) is a key mediator of these neural-specific extensions. Misexpression of ELAV results in the ectopicsynthesis of long messenger RNAs (mRNAs) in transgenic embryos. RNA immunoprecipitation assays suggest that ELAV directlybinds the proximal polyadenylation signals of many target mRNAs. Finally, ELAV is sufficient to suppress 3′ end formationat a strong polyadenylation signal when tethered to a synthetic RNA. We propose that this mechanism for coordinating 3′ UTRextension may be generally used in a variety of cellular processes
Very cold and massive cores near ISOSS J18364-0221: Implications for the initial conditions of high-mass star-formation
We report the discovery of two very cold and massive molecular cloud cores in
the region ISOSS J18364-0221. The object has been identified by a systematic
search for very early evolutionary stages of high-mass stars using the 170
micron ISOPHOT Serendipity Survey (ISOSS). Submm continuum and molecular line
measurements reveal two compact cores within this region. The first core has a
temperature of 16.5 K, shows signs of ongoing infall and outflows, has no NIR
or MIR counterpart and is massive enough (M ~ 75 M_sun) to form at least one O
star with an associated cluster. It is therefore considered a candidate for a
genuine high-mass protostar and a high-mass analog to the Class 0 objects. The
second core has an average gas and dust temperature of only ~ 12 K and a mass
of M ~ 280 M_sun. Its temperature and level of turbulence are below the values
found for massive cores so far and are suggested to represent the initial
conditions from which high-mass star formation occurs.Comment: 9 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Best possible densities of Dickson m-tuples, as a consequence of Zhang-Maynard-Tao
We determine for what proportion of integers one now knows that there are
infinitely many prime pairs as a consequence of the Zhang-Maynard-Tao
theorem. We consider the natural generalization of this to -tuples of
integers, and we determine the limit of what can be deduced assuming only the
Zhang-Maynard-Tao theorem.Comment: 9 pages. Final version. Some minor changes, Analytic Number Theory -
In Honor of Helmut Maier's 60th Birthday, Springer, 201
Part Count: Monolithic Part Effects on Manufacturing Labor Cost, an Aircraft Applied Model
There are significantly different manufacturing processes and part counts associated with composites that are not currently addressed within the aircraft procurement and life cycle management processes in the Department of Defense (DoD). A series of affordability initiatives have culminated in significant evidence over the last decade to better quantify the impact of primarily composite structures in aircraft. An Air Force Research Laboratory program, Advanced Composite Cargo Aircraft (ACCA), provides substantial support for the impact of part size on life cycle cost for payload aircraft. This research evaluates select methods used and seeks to introduce modifications to the projected manufacturing hours cost. The discussion addresses the far-reaching implications of trading several parts for one. This research finds that a significant relationship between relative part count and major cost categories does exist. Specifically, a percentage reduction in part count drives a corresponding percentage reduction in the manufacturing hours. Furthermore, the findings suggest the impact of monolithic parts appears to permeate most of the major cost categories in development and production. The series of findings pertaining to part count and cost merit consideration for updates to the current cost estimating relationships and interim modifications to capture some portion of the impact in current life cycle cost models
The utilization of television instruction in guidance at the sixth-grade level
Thesis (Ed.D.)--Boston Universit
Status of the isophot detector development
ISOPHOT is one of the four focal plane experiments of the European Space Agency's Infrared Space Observatory (ISO). Scheduled for a 1993 launch, it will operate extrinsic silicon and germanium photoconductors at low temperature and low background during the longer than 18 month mission. These detectors cover the wavelength range from 2.5 to 200 microns and are used as single elements and in arrays. A cryogenic preamplifier was developed to read out a total number of 223 detector pixels
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Emergent modular neural control drives coordinated motor actions.
A remarkable feature of motor control is the ability to coordinate movements across distinct body parts into a consistent, skilled action. To reach and grasp an object, 'gross' arm and 'fine' dexterous movements must be coordinated as a single action. How the nervous system achieves this coordination is currently unknown. One possibility is that, with training, gross and fine movements are co-optimized to produce a coordinated action; alternatively, gross and fine movements may be modularly refined to function together. To address this question, we recorded neural activity in the primary motor cortex and dorsolateral striatum during reach-to-grasp skill learning in rats. During learning, the refinement of fine and gross movements was behaviorally and neurally dissociable. Furthermore, inactivation of the primary motor cortex and dorsolateral striatum had distinct effects on skilled fine and gross movements. Our results indicate that skilled movement coordination is achieved through emergent modular neural control
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