2,799 research outputs found
Discovery of the Youngest Molecular Outflow associated with an Intermediate-mass protostellar Core, MMS-6/OMC-3
We present sub-arcsecond resolution HCN (4-3) and CO (3-2) observations made
with the Submillimeter Array (SMA), toward an extremely young intermediate-mass
protostellar core, MMS 6-main, located in the Orion Molecular Cloud 3 region
(OMC-3). We have successfully imaged a compact molecular outflow lobe (~1500
AU) associated with MMS6-main, which is also the smallest molecular outflow
ever found in the intermediate-mass protostellar cores. The dynamical time
scale of this outflow is estimated to be <100 yr. The line width dramatically
increases downstream at the end of the molecular outflow ({\Delta}v~25 km
s^{-1}), and clearly shows the bow-shock type velocity structure. The estimated
outflow mass (~10^{-4} M_{sun}) and outflow size are approximately 2-4 orders
and 1-3 orders of magnitude smaller, while the outflow force (~10^{-4} M_{sun}
km s^{-1} yr^{-1}) is similar, as compared to the other molecular outflows
studied in OMC-2/3. These results show that MMS 6-main is a protostellar core
at the earliest evolutionary stage, most likely shortly after the 2nd core
formation.Comment: Accepted to ApJ
An efficient and spectrally accurate numerical method for computing dynamics of rotating Bose-Einstein condensates
In this paper, we propose an efficient and spectrally accurate numerical
method for computing the dynamics of rotating Bose-Einstein condensates (BEC)
in two dimensions (2D) and 3D based on the Gross-Pitaevskii equation (GPE) with
an angular momentum rotation term. By applying a time-splitting technique for
decoupling the nonlinearity and properly using the alternating direction
implicit (ADI) technique for the coupling in the angular momentum rotation term
in the GPE, at every time step, the GPE in rotational frame is decoupled into a
nonlinear ordinary differential equation (ODE) and two partial differential
equations with constant coefficients. This allows us to develop new
time-splitting spectral (TSSP) methods for computing the dynamics of BEC in a
rotational frame.The new numerical method is explicit, unconditionally stable,
and of spectral accuracy in space and second order accuracy in time. Moreover,
it is time reversible and time transverse invariant, and conserves the position
density in the discretized level if the GPE does. Extensive numerical results
are presented to confirm the above properties of the new numerical method for
rotating BEC in 2D and 3D.Comment: 21 pages; 7 figure
Reconstruction of 3D Surface Maps from Anterior Segment Optical Coherence Tomography Images Using Graph Theory and Genetic Algorithms
Automatic segmentation of anterior segment optical coherence tomography images provides an important tool to aid management of ocular diseases. Previous studies have mainly focused on 2D segmentation of these images. A novel technique capable of producing 3D maps of the anterior segment is presented here. This method uses graph theory and dynamic programming with shape constraint to segment the anterior and posterior surfaces in individual 2D images. Genetic algorithms are then used to align 2D images to produce a full 3D representation of the anterior segment. In order to validate the results of the 2D segmentation comparison is made to manual segmentation over a set of 39 images. For the 3D reconstruction a data set of 17 eyes is used. These have each been imaged twice so a repeatability measurement can be made. Good agreement was found with manual segmentation for the 2D segmentation method achieving a Dice similarity coefficient of 0.96, which is comparable to the inter-observer agreement. Good repeatability of results was demonstrated with the 3D registration method. A mean difference of 1.77 pixels was found between the anterior surfaces found from repeated scans of the same eye
High Frequency Measurement of Temperature and Composition Spots with LITGS
Temperature and composition spots in a turbulent flow are detected and time-resolved using laser-induced thermal grating spectroscopy (LITGS). A 355 nm wavelength particle image velocimetry laser is operated at 0.5–1 kHz to generate the thermal grating using biacetyl as an absorber in trace amounts. In an open laminar jet, a feasibility study shows that small (≃ 3%) fluctuations in the mean flow properties are well captured with LITGS. However, corrections of the mean flow properties by the presence of the trace biacetyl are necessary to properly capture the fluctuations. The actual density and temperature variation in the flow are determined using a calibration procedure validated using a laminar jet flow. Finally, traveling entropy and composition spots are directly measured at different locations along a quartz tube, obtaining good agreement with expected values. This study demonstrates that LITGS can be used as a technique to obtain instantaneous, unsteady temperature and density variations in a combustion chamber, requiring only limited optical access.EPSRC, Qualcom
PolymiRTS Database: linking polymorphisms in microRNA target sites with complex traits
Polymorphism in microRNA Target Site (PolymiRTS) database is a collection of naturally occurring DNA variations in putative microRNA target sites. PolymiRTSs may affect gene expression and cause variations in complex phenotypes. The database integrates sequence polymorphism, phenotype and expression microarray data, and characterizes PolymiRTSs as potential candidates responsible for the quantitative trait locus (QTL) effects. It is a resource for studying PolymiRTSs and their implications in phenotypic variations. PolymiRTS database can be accessed at
Benefits and limitations of text messages to stimulate higher learning among community providers: participants’ views of an mHealth intervention to support continuing medical education in Vietnam
BACKGROUND: A randomized controlled trial was conducted in 2015 to evaluate a mobile continuing medical education (mCME) intervention that provided daily text messages to community-based physicians’ assistants (CBPAs) in Thai Nguyen Province, Vietnam. Although the intervention failed to improve medical knowledge over a 6-month period, a companion qualitative study provided insights on the views and experiences of intervention participants.
METHODS: We conducted focus group discussions (FGDs) and in-depth interviews (IDIs) among participants randomized to receive text messages containing either simple medical facts or quiz questions. Trained interviewers collected data immediately following the conclusion of the trial in December 2015. Using semi-structured question guides, respondents were queried on their views of the intervention, positive and negative, and perceived impacts of the intervention. During analysis, after learning that the intervention had failed to increase knowledge among participants, we also examined reasons for lack of improvement in medical knowledge. All analyses were performed in NVivo using a thematic approach.
RESULTS: A total of 70 CBPAs engaged in one of 8 FGDs or an IDI. One-half were men; average age among all respondents was 40 years. Most (81%) practiced in rural settings and most (51%) focused on general medicine. The mean length of work experience was 3 years. All respondents made positive comments about the intervention; convenience, relevance, and quick feedback (quiz format) were praised. Downsides encompassed lack of depth of information, weak interaction, technology challenges, and challenging/irrelevant messages. Respondents described perceived impacts encompassing increased motivation, knowledge, collegial discussions, Internet use to search for more information, and clinical skills. Overall, they expressed a desire for the intervention to continue and recommended expansion to other medical professionals. Overreliance on the text messages, lack of effective self-study, and technical/language-based barriers may be potential explanations for intervention failure.
CONCLUSION: As a form of mCME, daily text messages were well-received by community-level health care providers in Vietnam. This mCME approach appears very promising in low-resource environments or where traditional forms of CME are impractical. Future models might consider enhancements to foster linkages to relevant medical materials, improve interaction with medical experts, and tailor medical content to the daily activities of medical staff
Electronic vapor product use and suicidal behavior in adolescents
Objective: To determine whether an association exists between electronic vapor product use (EVP) and suicidal behavior in middle and high school students
Methods: Multilevel logistic regression analysis for suicidal behaviors using data from the 2017 Vermont Youth Risk Behavior Survey.
Results: Middle school EVP users were significantly more likely to report suicidal behavior than non-users. No statistically significant association was found in high school students.
Discussion: While further study is necessary to clarify the relationship between EVP use and suicidal behavior, these findings highlight the need for suicide prevention and smoking cessation efforts
Observation of kink instability during small B5.0 solar flare on 04 June, 2007
Using multi-wavelength observations of SoHO/MDI, SOT-Hinode/blue-continuum
(4504 \AA), G-band (4305 \AA), Ca II H (3968 \AA) and TRACE 171 \AA, we present
the observational signature of highly twisted magnetic loop in AR 10960 during
the period 04:43 UT-04:52 UT at 4 June, 2007. SOT-Hinode/blue-continuum (4504
\AA) observations show that penumbral filaments of positive polarity sunspot
have counter-clock wise twist, which may be caused by the clock-wise rotation
of the spot umbrae. The coronal loop, whose one footpoint is anchored in this
sunspot, shows strong right-handed twist in chromospheric SOT-Hinode/Ca II H
(3968 \AA) and coronal TRACE 171 \AA\, images. The length and the radius of the
loop are 80 Mm and 4.0 Mm respectively. The distance between
neighboring turns of magnetic field lines (i.e. pitch) is estimated as
10 Mm. The total twist angle, 12 (estimated for the
homogeneous distribution of the twist along the loop), is much larger than the
Kruskal -Shafranov instability criterion. We detected clear double structure of
the loop top during 04:47-04:51 UT on TRACE 171 \AA \ images, which is
consistent with simulated kink instability in curved coronal loops
(T{\"o}r{\"o}k et al. 2004). We suggest, that the kink instability of this
twisted magnetic loop triggered B5.0 class solar flare, which occurred between
04:40 UT and 04:51 UT in this active region.Comment: 24 pages, 5 Figures; The Astrophysical Journa
Evidence for short range orbital order in paramagnetic insulating (Al,V)_2O_3
The local structure of (Al_0.06V_0.94)_2O_3 in the paramagnetic insulating
(PI) and antiferromagnetically ordered insulating (AFI) phase has been
investigated using hard and soft x-ray absorption techniques. It is shown that:
1) on a local scale, the symmetry of the vanadium sites in both the PI and the
AFI phase is the same; and 2) the vanadium 3d - oxygen 2p hybridization, as
gauged by the oxygen 1s absorption edge, is the same for both phases, but
distinctly different from the paramagnetic metallic phase of pure V_2O_3. These
findings can be understood in the context of a recently proposed model which
relates the long range monoclinic distortion of the antiferromagnetically
ordered state to orbital ordering, if orbital short range order in the PI phase
is assumed. The measured anisotropy of the x-ray absorption spectra is
discussed in relation to spin-polarized density functional calculations.Comment: 8 pages, 5 figure
Quantum transport in double-gated graphene devices
Double-gated graphene devices provide an important platform for understanding
electrical and optical properties of graphene. Here we present transport
measurements of single layer, bilayer and trilayer graphene devices with
suspended top gates. In zero magnetic fields, we observe formation of pnp
junctions with tunable polarity and charge densities, as well as a tunable band
gap in bilayer graphene and a tunable band overlap in trilayer graphene. In
high magnetic fields, the devices' conductance are quantized at integer and
fractional values of conductance quantum, and the data are in good agreement
with a model based on edge state equilibration at pn interfaces
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