2,732 research outputs found
The COMPLETE Survey of Outflows in Perseus
We present a study on the impact of molecular outflows in the Perseus
molecular cloud complex using the COMPLETE survey large-scale 12CO(1-0) and
13CO(1-0) maps. We used three-dimensional isosurface models generated in
RA-DEC-Velocity space to visualize the maps. This rendering of the molecular
line data allowed for a rapid and efficient way to search for molecular
outflows over a large (~ 16 sq. deg.) area. Our outflow-searching technique
detected previously known molecular outflows as well as new candidate outflows.
Most of these new outflow-related high-velocity features lie in regions that
have been poorly studied before. These new outflow candidates more than double
the amount of outflow mass, momentum, and kinetic energy in the Perseus cloud
complex. Our results indicate that outflows have significant impact on the
environment immediately surrounding localized regions of active star formation,
but lack the energy needed to feed the observed turbulence in the entire
Perseus complex. This implies that other energy sources, in addition to
protostellar outflows, are responsible for turbulence on a global cloud scale
in Perseus. We studied the impact of outflows in six regions with active star
formation within Perseus of sizes in the range of 1 to 4 pc. We find that
outflows have enough power to maintain the turbulence in these regions and
enough momentum to disperse and unbind some mass from them. We found no
correlation between outflow strength and star formation efficiency for the six
different regions we studied, contrary to results of recent numerical
simulations. The low fraction of gas that potentially could be ejected due to
outflows suggests that additional mechanisms other than cloud dispersal by
outflows are needed to explain low star formation efficiencies in clusters.Comment: Published in The Astrophysical Journa
Emerging Data on Sorority/Fraternity-affiliated Student Government Presidents
Alongside sorority/fraternity governance structures, student government is another major form of campus involvement and student representation. At times, students share both student/leadership identities: as members of a sorority/fraternity and serving as a student government officer. In this study on student government presidents, descriptive statistics were used to tell the story of student government presidents who are also members of a sorority or fraternity and in comparison, to those who are not. Findings include present-day affiliation data, as well as campus contextual elements of their experience. There are subsequent recommendations for student affairs practice
The Effect of Projection on Derived Mass-Size and Linewidth-Size Relationships
Power law mass-size and linewidth-size correlations, two of "Larson's laws,"
are often studied to assess the dynamical state of clumps within molecular
clouds. Using the result of a hydrodynamic simulation of a molecular cloud, we
investigate how geometric projection may affect the derived Larson
relationships. We find that large scale structures in the column density map
have similar masses and sizes to those in the 3D simulation (PPP). Smaller
scale clumps in the column density map are measured to be more massive than the
PPP clumps, due to the projection of all emitting gas along lines of sight.
Further, due to projection effects, structures in a synthetic spectral
observation (PPV) may not necessarily correlate with physical structures in the
simulation. In considering the turbulent velocities only, the linewidth-size
relationship in the PPV cube is appreciably different from that measured from
the simulation. Including thermal pressure in the simulated linewidths imposes
a minimum linewidth, which results in a better agreement in the slopes of the
linewidth-size relationships, though there are still discrepancies in the
offsets, as well as considerable scatter. Employing commonly used assumptions
in a virial analysis, we find similarities in the computed virial parameters of
the structures in the PPV and PPP cubes. However, due to the discrepancies in
the linewidth- and mass- size relationships in the PPP and PPV cubes, we
caution that applying a virial analysis to observed clouds may be misleading
due to geometric projection effects. We speculate that consideration of
physical processes beyond kinetic and gravitational pressure would be required
for accurately assessing whether complex clouds, such as those with highly
filamentary structure, are bound.Comment: 25 pages, including 7 Figures; Accepted for publication in Ap
A New Approach to Developing Interactive Software Modules Through Graduate Education
Educational technology has attained significant importance as a mechanism for supporting experiential learning of science concepts. However, the growth of this mechanism is limited by the significant time and technical expertise needed to develop such products, particularly in specialized fields of science. We sought to test whether interactive, educational, online software modules can be developed effectively by students as a curriculum component of an advanced science course. We discuss a set of 15 such modules developed by Harvard University graduate students to demonstrate various concepts related to astronomy and physics. Their successful development of these modules demonstrates that online software tools for education and outreach on specialized topics can be produced while simultaneously fulfilling project-based learning objectives. We describe a set of technologies suitable for module development and present in detail four examples of modules developed by the students. We offer recommendations for incorporating educational software development within a graduate curriculum and conclude by discussing the relevance of this novel approach to new online learning environments like edX.Astronom
Measurement of mutual inductance from frequency dependence of impedance of AC coupled circuit using digital dual-phase lock-in amplifier
We present a simple method to determine the mutual inductance between two
coils in a coupled AC circuit by using a digital dual-phase lock-in amplifier.
The frequency dependence of the real and imaginary parts is measured as the
coupling constant is changed. The mutual inductance decreases as the
distance between the centers of coils is increased. We show that the
coupling constant is proportional to with an exponent (
3). This coupling is similar to that of two magnetic moments coupled through a
dipole-dipole interaction.Comment: 9 pages, 10 figures, Fig.1 is corrected, figures in png files, short
version is published in Am. J. Phys. 76, (2008) 12
Ethical, legal and social issues for personal health records and applications
AbstractRobert Wood Johnson Foundation’s Project HealthDesign included funding of an ethical, legal and social issues (ELSI) team, to serve in an advisory capacity to the nine design projects. In that capacity, the authors had the opportunity to analyze the personal health record (PHR) and personal health application (PHA) implementations for recurring themes. PHRs and PHAs invert the long-standing paradigm of health care institutions as the authoritative data-holders and data-processors in the system. With PHRs and PHAs, the individual is the center of his or her own health data universe, a position that brings new benefits but also entails new responsibilities for patients and other parties in the health information infrastructure. Implications for law, policy and practice follow from this shift. This article summarizes the issues raised by the first phase of Project HealthDesign projects, categorizing them into four topics: privacy and confidentiality, data security, decision support, and HIPAA and related legal-regulatory requirements. Discussion and resolution of these issues will be critical to successful PHR/PHA implementations in the years to come
Beyond June: (Re)Visiting Sorority/Fraternity Messages About LGBTQ+ Identities and Issues from 2020 - 2021
In this critical discourse analysis (CDA), we examine 140 inter/national social sorority and fraternity organizations and their messages– and lack thereof–regarding lesbian, gay, bisexual, transgender, and queer (LGBTQ+) identities and issues. Just 1.24% (507) of total posts (40,778) during 2020-2021 were about LGBTQ+ identities and issues. Despite the immense increase in LGBTQ+ recognition for most sororities and fraternities during Pride Month (June), CDA allowed us a criticality of these messages, both within and outside of Pride Month. Recommendations include being explicit about “LGBTQ+” framing, and also call for continued research to understand how organizations and members engage online
A Photometrically and Morphologically Variable Infrared Nebula in L483
We present narrow and broad K-band observations of the Class 0/I source IRAS
18148-0440 that span 17 years. The infrared nebula associated with this
protostar in the L483 dark cloud is both morphologically and photometrically
variable on a time scale of only a few months. This nebula appears to be an
infrared analogue to other well-known optically visible variable nebulae
associated with young stars, such as Hubble's Variable Nebula. Along with
Cepheus A, this is one of the first large variable nebulae to be found that is
only visible in the infrared. The variability of this nebula is most likely due
to changing illumination of the cloud rather than any motion of the structure
in the nebula. Both morphological and photometric changes are observed on a
time scale only a few times longer than the light crossing time of the nebula,
suggesting very rapid intrinsic changes in the illumination of the nebula. Our
narrow-band observations also found that H_2 knots are found nearly twice as
far to the east of the source as to its west, and that H_2 emission extends
farther east of the source than the previously known CO outflow.Comment: 19 pages, 6 figures, 1 tabl
Multigrid Monte Carlo Algorithms for SU(2) Lattice Gauge Theory: Two versus Four Dimensions
We study a multigrid method for nonabelian lattice gauge theory, the time
slice blocking, in two and four dimensions. For SU(2) gauge fields in two
dimensions, critical slowing down is almost completely eliminated by this
method. This result is in accordance with theoretical arguments based on the
analysis of the scale dependence of acceptance rates for nonlocal Metropolis
updates. The generalization of the time slice blocking to SU(2) in four
dimensions is investigated analytically and by numerical simulations. Compared
to two dimensions, the local disorder in the four dimensional gauge field leads
to kinematical problems.Comment: 24 pages, PostScript file (compressed and uuencoded), preprint
MS-TPI-94-
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