965 research outputs found
A System Application to The Classical Functions of Managements
This study compares the traditional approach to the functions of management with the systems approach these same functions, an examination and tabulation of classical management functions is conducted, this approach is then contrasted and compared current innovations in the system concept of management, A model is developed show how systems thinking applies in a classical structure, Overall, it is concluded that the systems approach does have validity of application
Analysis of simple 2-D and 3-D metal structures subjected to fragment impact
Theoretical methods were developed for predicting the large-deflection elastic-plastic transient structural responses of metal containment or deflector (C/D) structures to cope with rotor burst fragment impact attack. For two-dimensional C/D structures both, finite element and finite difference analysis methods were employed to analyze structural response produced by either prescribed transient loads or fragment impact. For the latter category, two time-wise step-by-step analysis procedures were devised to predict the structural responses resulting from a succession of fragment impacts: the collision force method (CFM) which utilizes an approximate prediction of the force applied to the attacked structure during fragment impact, and the collision imparted velocity method (CIVM) in which the impact-induced velocity increment acquired by a region of the impacted structure near the impact point is computed. The merits and limitations of these approaches are discussed. For the analysis of 3-d responses of C/D structures, only the CIVM approach was investigated
Finite-element nonlinear transient response computer programs PLATE 1 and CIVM-PLATE 1 for the analysis of panels subjected to impulse or impact loads
Two computer programs are described for predicting the transient large deflection elastic viscoplastic responses of thin single layer, initially flat unstiffened or integrally stiffened, Kirchhoff-Lov ductile metal panels. The PLATE 1 program pertains to structural responses produced by prescribed externally applied transient loading or prescribed initial velocity distributions. The collision imparted velocity method PLATE 1 program concerns structural responses produced by impact of an idealized nondeformable fragment. Finite elements are used to represent the structure in both programs. Strain hardening and strain rate effects of initially isotropic material are considered
User's guide to computer programs JET 5A and CIVM-JET 5B to calculate the large elastic-plastic dynamically-induced deformations of multilayer partial and/or complete structural rings
These structural ring deflections lie essentially in one plane and, hence, are called two-dimensional (2-d). The structural rings may be complete or partial; the former may be regarded as representing a fragment containment ring while the latter may be viewed as a 2-d fragment-deflector structure. These two types of rings may be either free or supported in various ways (pinned-fixed, locally clamped, elastic-foundation supported, mounting-bracket supported, etc.). The initial geometry of each ring may be circular or arbitrarily curved; uniform-thickness or variable-thickness rings may be analyzed. Strain-hardening and strain-rate effects of initially-isotropic material are taken into account. An approximate analysis utilizing kinetic energy and momentum conservation relations is used to predict the after-impact velocities of each fragment and of the impact-affected region of the ring; this procedure is termed the collision-imparted velocity method (CIVM) and is used in the CIVM-JET 5 B program. This imparted-velocity information is used in conjunction with a finite-element structural response computation code to predict the transient, large-deflection, elastic-plastic responses of the ring. Similarly, the equations of motion of each fragment are solved in small steps in time. Provisions are made in the CIVM-JET 5B code to analyze structural ring response to impact attack by from 1 to 3 fragments, each with its own size, mass, translational velocity components, and rotational velocity. The effects of friction between each fragment and the impacted ring are included
Massive quenched galaxies at z~0.7 retain large molecular gas reservoirs
The physical mechanisms that quench star formation, turning blue star-forming
galaxies into red quiescent galaxies, remain unclear. In this Letter, we
investigate the role of gas supply in suppressing star formation by studying
the molecular gas content of post-starburst galaxies. Leveraging the wide area
of the SDSS, we identify a sample of massive intermediate-redshift galaxies
that have just ended their primary epoch of star formation. We present ALMA
CO(2-1) observations of two of these post-starburst galaxies at z~0.7 with M* ~
2x10^11 Msun. Their molecular gas reservoirs of (6.4 +/- 0.8) x 10^9 Msun and
(34.0 +/- 1.6) x 10^9 Msun are an order of magnitude larger than
comparable-mass galaxies in the local universe. Our observations suggest that
quenching does not require the total removal or depletion of molecular gas, as
many quenching models suggest. However, further observations are required both
to determine if these apparently quiescent objects host highly obscured star
formation and to investigate the intrinsic variation in the molecular gas
properties of post-starburst galaxies.Comment: Accepted for publication in ApJ Letters (6 pages, 5 figures
An Analysis of ALMA Deep Fields and the Perceived Dearth of High-z Galaxies
Deep, pencil-beam surveys from ALMA at 1.1-1.3mm have uncovered an apparent
absence of high-redshift dusty galaxies, with existing redshift distributions
peaking around . This has led to a perceived dearth of dusty
systems at , and the conclusion, according to some models, that the early
Universe was relatively dust-poor. In this paper, we extend the backward
evolution galaxy model described by Casey et al. (2018) to the ALMA regime (in
depth and area) and determine that the measured number counts and redshift
distributions from ALMA deep field surveys are fully consistent with
constraints of the infrared luminosity function (IRLF) at determined by
single-dish submillimeter and millimeter surveys conducted on much larger
angular scales (deg). We find that measured 1.1-1.3mm number
counts are most constraining for the measurement of the faint-end slope of the
IRLF at . Recent
studies have suggested that UV-selected galaxies at may be particularly
dust-poor, but we find their millimeter-wave emission cannot rule out
consistency with the Calzetti dust attenuation law even by assuming relatively
typical, cold-dust (K) SEDs. Our models suggest that
the design of ALMA deep fields requires substantial revision to constrain the
prevalence of early Universe obscured starbursts. The most promising
avenue for detection and characterization of such early dusty galaxies will
come from future ALMA 2mm blank field surveys covering a few hundred
arcmin and the combination of existing and future dual-purpose 3mm
datasets.Comment: 21 pages, 12 figures, accepted for publication in Ap
Caenorhabditis elegans Muscleblind homolog mbl-1 functions in neurons to regulate synapse formation
<p>Abstract</p> <p>Background</p> <p>The sequestration of Muscleblind splicing regulators results in myotonic dystrophy. Previous work on Muscleblind has largely focused on its roles in muscle development and maintenance due to the skeletal and cardiac muscle degeneration phenotype observed in individuals with the disorder. However, a number of reported nervous system defects suggest that Muscleblind proteins function in other tissues as well.</p> <p>Results</p> <p>We have identified a mutation in the <it>Caenorhabditis elegans </it>homolog of Muscleblind, <it>mbl-1</it>, that is required for proper formation of neuromuscular junction (NMJ) synapses. <it>mbl-1 </it>mutants exhibit selective loss of the most distal NMJ synapses in a <it>C. elegans </it>motorneuron, DA9, visualized using the vesicle-associated protein RAB-3, as well as the active zone proteins SYD-2/liprin-α and UNC-10/Rim. The proximal NMJs appear to have normal pre- and postsynaptic specializations. Surprisingly, expressing a <it>mbl-1 </it>transgene in the presynaptic neuron is sufficient to rescue the synaptic defect, while muscle expression has no effect. Consistent with this result, <it>mbl-1 </it>is also expressed in neurons.</p> <p>Conclusions</p> <p>Based on these results, we conclude that in addition to its functions in muscle, the Muscleblind splice regulators also function in neurons to regulate synapse formation.</p
Scientific Value of a Saturn Atmospheric Probe Mission
Atmospheric entry probe mISSions to the giant planets can uniquely discriminate between competing theories of solar system formation and the origin and evolution of the giant planets and their atmospheres. This provides for important comparative studies of the gas and ice giants, and to provide a laboratory for studying the atmospheric chemistries, dynamics, and interiors of all the planets including Earth. The giant planets also represent a valuable link to extrasolar planetary systems. As outlined in the recent Planetary Decadal Survey, a Saturn Probe mission - with a shallow probe - ranks as a high priority for a New Frontiers class mission [1]
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Scientific rationale of a Saturn probe mission
We describe the main scientific goals to be addressed by future in situ exploration of Saturn
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