9,755 research outputs found
Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
We present a combined analysis of the low-mass Initial Mass Function (IMF)
for seven star forming regions. We first demonstrate that the ratios of stars
to brown dwarfs are consistent with a single underlying IMF. Assuming the
underlying IMF is the same for all seven clusters and by combining the ratio of
stars to brown dwarfs from each cluster we constrain the shape of the brown
dwarf IMF and find it to be consistent with a log--normal IMF. This provides
the strongest constraint yet that the sub-stellar IMF turns over (dN/dM
M^(-alpha), alpha < 0).Comment: 12 pages, 2 figures. Accepted in ApJ Letters Revised version have
Column 7 modified from previous versions and gramatical errors have been
correcte
Arbitrary Ranking of Defeasible Subsumption
In this paper we propose an algorithm that generalises existing procedures for the implementation of defeasible reasoning in the framework of Description Logics (DLs). One of the well-known approaches to defeasible reasoning, the so-called KLM approach, is based on constructing specific rankings of defeasible information, and using these rankings to determine priorities in case of conflicting information. Here we propose a procedure that allows us to input any possible ranking of the defeasible concept inclusions contained in the knowledge base. We analyse and investigate the forms of defeasible reasoning obtained when conclusions drawn are obtained using these rankings
A Marginal Identity Model for those in the In-Between
Background
In existing models exploring the formation cultural identity, there is emphasis on development from the perspective of race or country of origin. While these models have made significant contributions to the study of identity development in the fields of counseling and psychology, research on the identity development of people who exist within the spectrum between traditionally acknowledged identities (Deaf/Hearing, LGBTQIA+, first/second generation) is lacking. Methods
To explore the merit of establishing a distinct theory exploring development of individuals whose identities exist between the existing binaries of identity, a systematic review and analysis of current literature was performed. Subsequently, a framework for marginal identity to address present gaps in literature was developed. The information from the review was integrated, and a hypothesis based on the framework was formed. Data from recent studies on multicultural/marginal development was gathered to corroborate or refute this hypothesis. Results
The Marginal/Multicultural Identity Model developed by Reid et al. addresses groups that exist in the “in between” of the continuum of identity. Building on previous models of identity development, this model addresses the fluid and nonlinear nature of identity, as well as the impact of environmental, personal, physical, and intersectional factors, while also considering the knowledge and skills required in a given culture.
4. Conclusion
This model has potential to address a missing element in counseling practice: addressing the needs of people who find themselves between different cultures. Further research is needed to test the effectiveness of the model in actual clinical trials.https://scholarscompass.vcu.edu/gradposters/1173/thumbnail.jp
Tracking Different Ant Species: An Unsupervised Domain Adaptation Framework and a Dataset for Multi-object Tracking
Tracking individuals is a vital part of many experiments conducted to
understand collective behaviour. Ants are the paradigmatic model system for
such experiments but their lack of individually distinguishing visual features
and their high colony densities make it extremely difficult to perform reliable
tracking automatically. Additionally, the wide diversity of their species'
appearances makes a generalized approach even harder. In this paper, we propose
a data-driven multi-object tracker that, for the first time, employs domain
adaptation to achieve the required generalisation. This approach is built upon
a joint-detection-and-tracking framework that is extended by a set of domain
discriminator modules integrating an adversarial training strategy in addition
to the tracking loss. In addition to this novel domain-adaptive tracking
framework, we present a new dataset and a benchmark for the ant tracking
problem. The dataset contains 57 video sequences with full trajectory
annotation, including 30k frames captured from two different ant species moving
on different background patterns. It comprises 33 and 24 sequences for source
and target domains, respectively. We compare our proposed framework against
other domain-adaptive and non-domain-adaptive multi-object tracking baselines
using this dataset and show that incorporating domain adaptation at multiple
levels of the tracking pipeline yields significant improvements. The code and
the dataset are available at https://github.com/chamathabeysinghe/da-tracker
Semi-Automatic, Inline and Collaborative Web Page Code Curations
Software developers spend about a quarter of their workday using the web to fulfill various information needs. Searching for relevant information online can be time-consuming, yet acquired information is rarely systematically persisted for later reference. In this work, we introduce SALI, an approach for semi-automated linking web pages to source code locations inline with the source code. SALI helps developers naturally capture high-quality, explicit links between web pages and specific source code locations by suggesting links for curation within the IDE. Through two laboratory studies, we examined the developer’s ability to both curate and consume links between web pages and specific source code locations while performing software development tasks. The studies were performed with 20 subjects working on realistic software change tasks from widely-used open-source projects. Results showed that developers continuously and concisely curate web pages at meaningful locations in the code with little effort. Additionally, we showed that other developers could use these curations while performing new and different change tasks to speed up relevant information gathering within unfamiliar codebases by a factor of 2.4
Occultation of the Quiescent Emission from Sgr A* by IR Flares
We have investigated the nature of flare emission from Sgr A* during
multi-wavelength observations of this source that took place in 2004, 2005 and
2006. We present evidence for dimming of submm and radio flux during the peak
of near-IR flares. This suggests that the variability of Sgr A* across its
wavelength spectrum is phenomenologically related. The model explaining this
new behavior of flare activity could be consistent with adiabatically cooling
plasma blobs that are expanding but also partially eclipsing the background
quiescent emission from Sgr A*. When a flare is launched, the plasma blob is
most compact and is brightest in the optically thin regime whereas the emission
in radio/submm wavelengths has a higher opacity. Absorption in the observed
light curve of Sgr A* at radio/submm flux is due to the combined effects of
lower brightness temperature of plasma blobs with respect to the quiescent
brightness temperature and high opacity of plasma blobs. This implies that
plasma blobs are mainly placed in the magnetosphere of a disk-like flow or
further out in the flow. The depth of the absorption being larger in submm than
in radio wavelengths implies that the intrinsic size of the quiescent emission
increases with increasing wavelength which is consistent with previous size
measurements of Sgr A*. Lastly, we believe that occultation of the quiescent
emission of Sgr A* at radio/submm by IR flares can be used as a powerful tool
to identify flare activity at its earliest phase of its evolution.Comment: 11 pages, 5 figures, accepted by ApJ
Length of Need and Minimum System Length for F-Shape Portable Concrete Barrier
Portable concrete barrier (PCB) systems are often used to redirect errant vehicles through a combination of inertial resistance, lateral friction loads, and tensile loads developed from the mass and friction of the barrier segments. State departments of transportation (DOTs) and other end users may wish to utilize minimal length PCB installations to shield a hazard or work zone or limit the number of barriers required on the upstream and downstream ends to reduce overall system length. However, concerns with the performance of shorter PCB installations include increased lateral deflections and working widths and barrier pocketing. Additionally, no impact testing has been performed near the upstream or downstream ends of the free-standing PCB system to determine the limits of the length of need (LON) of the system. These impacts may increase the potential for gating through the system, pocketing, rapid deceleration, and/or vehicle instability.
The objective of this research study was to investigate and evaluate the safety performance of a previously developed F-shape PCB system to determine minimum system length and the number of barriers required for the beginning and end of the LON. LS-DYNA simulation modeling was applied to determine potential beginning and end of LON points on reduced system lengths to select a configuration for full-scale testing and evaluation of a minimum length PCB system. A 100-ft long PCB installation was selected, and full-scale crash testing was conducted on the beginning and end of LON of the reduced length system. Test no. NELON-1 was conducted to MASH test designation 3-35 criteria on the beginning of LON of the 100-ft long PCB installation, and the vehicle was safely redirected. Test no. NELON-2 was conducted to modified MASH test designation no. 3-37 criteria on the end of LON of the 100-ft long PCB installation, but the test was deemed a failure as the vehicle demonstrated a roll angle in excess of 75 degrees. Review of the crash test results suggested that a nine barrier or 112.5-ft long PCB installation would perform acceptably
A numerical study of the correspondence between paths in a causal set and geodesics in the continuum
This paper presents the results of a computational study related to the
path-geodesic correspondence in causal sets. For intervals in flat spacetimes,
and in selected curved spacetimes, we present evidence that the longest maximal
chains (the longest paths) in the corresponding causal set intervals
statistically approach the geodesic for that interval in the appropriate
continuum limit.Comment: To the celebration of the 60th birthday of Rafael D. Sorki
C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation
International audienceVoltage-gated Na(+) (NaV) channels are key regulators of myocardial excitability, and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1.5 proteins purified from adult WT and failing CaMKIIδc-overexpressing (CaMKIIδc-Tg) mouse ventricles. Of 19 native NaV1.5 phosphorylation sites identified, two C-terminal phosphoserines at positions 1938 and 1989 showed increased phosphorylation in the CaMKIIδc-Tg compared with the WT ventricles. We then tested the hypothesis that phosphorylation at these two sites impairs fibroblast growth factor 13 (FGF13)-dependent regulation of NaV1.5 channel inactivation. Whole-cell voltage-clamp analyses in HEK293 cells demonstrated that FGF13 increases NaV1.5 channel availability and decreases late Na(+) current, two effects that were abrogated with NaV1.5 mutants mimicking phosphorylation at both sites. Additional co-immunoprecipitation experiments revealed that FGF13 potentiates the binding of calmodulin to NaV1.5 and that phosphomimetic mutations at both sites decrease the interaction of FGF13 and, consequently, of calmodulin with NaV1.5. Together, we have identified two novel native phosphorylation sites in the C terminus of NaV1.5 that impair FGF13-dependent regulation of channel inactivation and may contribute to CaMKIIδc-dependent arrhythmogenic disorders in failing hearts
The low-mass Initial Mass Function in the Orion Nebula cluster based on HST/NICMOS III imaging
We present deep HST/NICMOS Camera 3 F110W and F160W imaging of a 26'x33',
corresponding to 3.1pcx3.8pc, non-contiguous field towards the Orion Nebula
Cluster (ONC). The main aim is to determine the ratio of low--mass stars to
brown dwarfs for the cluster as a function of radius out to a radial distance
of 1.5pc. The sensitivity of the data outside the nebulous central region is
F160W=21.0 mag, significantly deeper than previous studies of the region over a
comparable area. We create an extinction limited sample and determine the ratio
of low-mass stars (0.08-1Msun) to brown dwarfs (0.02-0.08Msun and
0.03-0.08Msun) for the cluster as a whole and for several annuli. The ratio
found for the cluster within a radius of 1.5pc is
R(02)=N(0.08-1Msun)/N(0.02-0.08Msun)=1.7+-0.2, and
R(03)=N(0.08-1Msun)/N(0.03-0.08Msun)=2.4+-0.2, after correcting for field
stars. The ratio for the central 0.3pcx0.3pc region down to 0.03Msun was
previously found to be R(03)=3.3+0.8-0.7, suggesting the low-mass content of
the cluster is mass segregated. We discuss the implications of a gradient in
the ratio of stars to brown dwarfs in the ONC in the context of previous
measurements of the cluster and for other nearby star forming regions. We
further discuss the current evidence for variations in the low-mass IMF and
primordial mass segregation.Comment: Accepted to A&
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