449 research outputs found
Developing Sustained Competitive Advantage: Business Process Reengineering versus Management of Information as a Resource
Information Technology induced Business Process Reengineering is being offered as a solution to organizations to achieve competitive advantage in an intensely competitive environment. However, just radical changes in business processes will not help an organization sustain competitive advantage as successful business process reengineering projects can be cloned by competing organizations, thereby negating the competitive advantage developed by any one organization. Instead, if an organization were to design and implement information systems for strategic management of information as a resource, then use of such systems can lead to sustainable competitive advantage. This paper presents the case for the use of an information system designed from the resource based perspective as a source of sustainablecompetitive advantage over business process reengineerin
SMA Imaging of the Maser Emission from the H30 Radio Recombination Line in MWC349A
We used the Submillimeter Array to map the angular distribution of the
H30 recombination line (231.9 GHz) in the circumstellar region of the
peculiar star MWC349A. The resolution was 1\farcs2, but because of high
signal-to-noise ratio we measured the positions of all maser components to
accuracies better than 0\farcs01, at a velocity resolution of . The
two strongest maser components (called high velocity components) at velocities
near -14 and are separated by 0\farcs048 \pm 0\farcs001 (60 AU)
along a position angle of 102 \pm 1\arcdeg. The distribution of maser
emission at velocities between and beyond these two strongest components were
also provided. The continuum emission lies at the center of the maser
distribution to within 10 mas. The masers appear to trace a nearly edge-on
rotating disk structure, reminiscent of the water masers in Keplerian rotation
in the nuclear accretion disk of the galaxy NGC4258. However, the maser
components in MWC349A do not follow a simple Keplerian kinematic prescription
with , but have a larger power law index. We explore the
possibility that the high velocity masers trace spiral density or shock waves.
We also emphasize caution in the interpretation of relative centroid maser
positions where the maser is not clearly resolved in position or velocity, and
we present simulations that illustrate the range of applicability of the
centroiding method.Comment: 23 pages with 9 figures (two of these figures are vertically aligned
as Figure 4) submitted to the Astrophysical Journa
In-vivo glenohumeral translation and ligament elongation during abduction and abduction with internal and external rotation
Study Design:
Basic Science. To investigate humeral head translations and glenohumeral ligament elongation with a dual fluoroscopic imaging system.
Background:
The glenohumeral ligaments are partially responsible for restraining the humeral head during the extremes of shoulder motion. However, in-vivo glenohumeral ligaments elongation patterns have yet to be determined. Therefore, the objectives of this study were to 1) quantify the in-vivo humeral head translations and glenohumeral ligament elongations during functional shoulder positions, 2) compare the inferred glenohumeral ligament functions with previous literature and 3) create a baseline data of healthy adult shoulder glenohumeral ligament lengths as controls for future studies.
Methods:
Five healthy adult shoulders were studied with a validated dual fluoroscopic imaging system (DFIS) and MR imaging technique. Humeral head translations and the superior, middle and inferior glenohumeral ligaments (SGHL, MGHL, IGHL) elongations were determined.
Results:
The humeral head center on average translated in a range of 6.0mm in the anterior-posterior direction and 2.5mm in the superior-inferior direction. The MGHL showed greater elongation over a broader range of shoulder motion than the SGHL. The anterior-band (AB)-IGHL showed maximum elongation at 90° abduction with maximum external rotation. The posterior-band (PB)-IGHL showed maximum elongation at 90° abduction with maximum internal rotation.
Discussion:
The results demonstrated that the humeral head translated statistically more in the anterior-posterior direction than the superior-inferior direction (p = 0.01), which supports the concept that glenohumeral kinematics are not ball-in-socket mechanics. The AB-IGHL elongation pattern makes it an important static structure to restrain anterior subluxation of the humeral head during the externally rotated cocking phase of throwing motion. These data suggest that in healthy adult shoulders the ligamentous structures of the glenohumeral joint are not fully elongated in many shoulder positions, but function as restraints at the extremes of glenohumeral motion. Clinically, these results may be helpful in restoring ligament anatomy during the treatment of anterior instability of the shoulder
Non-clasical Nucleation in Supercooled Nickel
The dynamics of homogeneous nucleation and growth of crystalline nickel from
the super-cooled melt is examined during rapid quenching using molecular
dynamics and a modified embedded atom method potential. The character of the
critical nuclei of the crystallization transition is examined using common
neighbor analysis and visualization. At nucleation the saddle point droplet
consists of randomly stacked planar structures with an in plane triangular
order. These results are consistent with previous theoretical results that
predict that the nucleation process in some metals is non-classical due to the
presence of long-range forces and a spinodal.Comment: 4 pages, 5 figure
SMA detection of an extreme millimeter flare from the young class III star HD 283572
We present evidence of variable 1.3 millimeter emission from the 1-3 Myr, SpT
G2-G5 class III YSO, HD~283572. HD~283572 was observed on 8 dates with the
Submillimeter Array between 2021 December and 2023 May, a total on-source time
of 10.2 hours, probing a range of timescales down to 5.2 seconds. Averaging all
data obtained on 2022 Jan 17 shows a 4.4 mJy () point source
detection with a negative spectral index (), with peak
emission rising to 13.8 mJy in one 3 minute span, and 25 mJy in one 29.7 second
integration ( erg s Hz). Combining our
data for the other 7 dates shows no detection, with an rms noise of 0.24 mJy
beam. The stochastic millimeter enhancements on time frames of
seconds--minutes--hours with negative spectral indices are most plausibly
explained by synchrotron or gyro-synchrotron radiation from stellar activity.
HD 283572's 1.3 mm light-curve has similarities with variable binaries,
suggesting HD 283572's activity may have been triggered by interactions with an
as-yet undetected companion. We additionally identify variability of HD 283572
at 10 cm, from VLASS data. This study highlights the challenges of interpreting
faint mm emission from evolved YSOs that may host tenuous disks, and suggests
that a more detailed temporal analysis of spatially unresolved data is
generally warranted. The variability of class III stars may open up new ground
for understanding the physics of flares in the context of terrestrial planet
formation.Comment: Accepted for publication in ApJL. 12 pages, inc. 5 figures, 2 table
The Submillimeter Polarization of Sgr A*
We report on the submillimeter properties of Sagittarius A* derived from
observations with the Submillimeter Array and its polarimeter. We find that the
spectrum of Sgr A* between 230 and 690 GHz is slightly decreasing when measured
simultaneously, indicating a transition to optically thin emission around
300-400 GHz. We also present very sensitive and well calibrated measurements of
the polarization of Sgr A* at 230 and 345 GHz. With these data we are able to
show for the first time that the polarization of Sgr A* varies on hour
timescales, as has been observed for the total intensity. On one night we find
variability that may arise from a polarized "blob" orbiting the black hole.
Finally, we use the ensemble of observations to determine the rotation measure.
This represents the first statistically significant rotation measure
determination and the only one made without resorting to comparing position
angles measured at separate epochs. We find a rotation measure of
(-5.6+/-0.7)x10^5 rad/m^2, with no evidence for variability on inter-day
timescales at the level of the measurement error. The stability constrains
interday fluctuations in the accretion rate to 8%. The mean intrinsic
polarization position angle is 167+/-7 degrees and we detect variations of
31+18/-9 degrees. This separation of intrinsic polarization changes and
possible rotation measure fluctuations is now possible because of the frequency
coverage and sensitivity of our data. The observable rotation measure restricts
the accretion rate to the range 2x10^{-7} Msun/yr to 2x10^{-9} Msun/yr, if the
magnetic field is near equipartition and ordered.Comment: v2: Minor change to orbital calculation. Invited contribution to the
proceedings of the Galactic Center Workshop 200
Characterizing Magnetic Field Morphologies in Three Serpens Protostellar Cores with ALMA
With the aim of characterizing the dynamical processes involved in the formation of young protostars, we present high-angular-resolution ALMA dust polarization observations of the Class 0 protostellar cores Serpens SMM1, Emb 8(N), and Emb 8. With spatial resolutions ranging from 150 to 40 au at 870 μm, we find unexpectedly high values of the polarization fraction along the outflow cavity walls in Serpens Emb 8(N). We use 3 mm and 1 mm molecular tracers to investigate outflow and dense-gas properties and their correlation with the polarization. These observations allow us to investigate the physical processes involved in the radiative alignment torques (RATs) acting on dust grains along the outflow cavity walls, which experience irradiation from accretion processes and outflow shocks. The inner core of SMM1-a presents a polarization pattern with a poloidal magnetic field at the bases of the two lobes of the bipolar outflow. To the south of SMM1-a we see two polarized filaments, one of which seems to trace the redshifted outflow cavity wall. The other may be an accretion streamer of material infalling onto the central protostar. We propose that the polarized emission we see at millimeter wavelengths along the irradiated cavity walls can be reconciled with the expectations of RAT theory if the aligned grains present at <500 au scales in Class 0 envelopes have grown larger than the 0.1 μm size of dust grains in the interstellar medium. Our observations allow us to constrain the magnetic field morphologies of star-forming sources within the central cores, along the outflow cavity walls, and in possible accretion streamers
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