1,296 research outputs found
Transactional Distance in MOOCs: A Critical Analysis of Dialogue, Structure, and Learner Autonomy
Drawing upon a content analysis of studentsâ postings on CourseTalk.org, this study presents preliminary findings of analyzing transactional distance in xMOOCs in order to elucidate the educational exchange facilitated or restricted with reference to the three variables of transactional distance theory
Hot Stars and Cool Clouds: The Photodissociation Region M16
We present high-resolution spectroscopy and images of a photodissociation
region (PDR) in M16 obtained during commissioning of NIRSPEC on the Keck II
telescope. PDRs play a significant role in regulating star formation, and M16
offers the opportunity to examine the physical processes of a PDR in detail. We
simultaneously observe both the molecular and ionized phases of the PDR and
resolve the spatial and kinematic differences between them. The most prominent
regions of the PDR are viewed edge-on. Fluorescent emission from nearby stars
is the primary excitation source, although collisions also preferentially
populate the lowest vibrational levels of H2. Variations in density-sensitive
emission line ratios demonstrate that the molecular cloud is clumpy, with an
average density n = 3x10^5 cm^(-3). We measure the kinetic temperature of the
molecular region directly and find T_H2 = 930 K. The observed density,
temperature, and UV flux imply a photoelectric heating efficiency of 4%. In the
ionized region, n_i=5x10^3 cm^(-3) and T_HII = 9500 K. In the brightest regions
of the PDR, the recombination line widths include a non-thermal component,
which we attribute to viewing geometry.Comment: 5 pages including 2 Postscript figures. To appear in ApJ Letters,
April 200
Landau-Ginzburg Description of Boundary Critical Phenomena in Two Dimensions
The Virasoro minimal models with boundary are described in the
Landau-Ginzburg theory by introducing a boundary potential, function of the
boundary field value. The ground state field configurations become non-trivial
and are found to obey the soliton equations. The conformal invariant boundary
conditions are characterized by the reparametrization-invariant data of the
boundary potential, that are the number and degeneracies of the stationary
points. The boundary renormalization group flows are obtained by varying the
boundary potential while keeping the bulk critical: they satisfy new selection
rules and correspond to real deformations of the Arnold simple singularities of
A_k type. The description of conformal boundary conditions in terms of boundary
potential and associated ground state solitons is extended to the N=2
supersymmetric case, finding agreement with the analysis of A-type boundaries
by Hori, Iqbal and Vafa.Comment: 42 pages, 13 figure
Current state of scientific evidence on Internet-based interventions for the treatment of depression, anxiety, eating disorders and substance abuse: An overview of systematic reviews and meta-analyses
BACKGROUND: ICare represents a consortium of European Investigators examining the effects of online mental health care for a variety of common mental health disorders provided in a variety of settings. This article provides an overview of the evidence of effectiveness for Internet-based treatment for four common mental health disorders that are the focus of much of this work: depression, anxiety, substance abuse and eating disorders.
METHODS: The overview focused primarily on systematic reviews and meta-analyses identified through PubMed (Ovid) and other databases and published in English. Given the large number of reviews specific to depression, anxiety, substance abuse and/or eating disorders, we did not focus on reviews that examined the effects of Internet-based interventions on mental health disorders in general. Each article was reviewed and summarized by one of the senior authors, and this review was then reviewed by the other senior authors. We did not address issues of prevention, cost-effectiveness, implementation or dissemination, as these are addressed in other reviews in this supplement.
RESULTS: Across Internet-based intervention studies addressing depression, anxiety, substance abuse and eating disorders primarily among adults, almost all reviews and meta-analyses found that these interventions successfully reduce symptoms and are efficacious treatments. Generally, effect sizes for Internet-based interventions treating eating disorders and substance abuse are lower compared with interventions for depression and anxiety.
CONCLUSIONS: Given the effectiveness of Internet-based interventions to reduce symptoms of these common mental health disorders, efforts are needed to examine issues of how they can be best disseminated and implemented in a variety of health care and other settings
A systematic digital approach to implementation and dissemination of eating disorders interventions to large populations identified through online screening: Implications for post-traumatic stress
Background: We describe an approach to implementation and dissemination that focuses on changing outcomes variables within a large, defined population and attempts to provide cost-effective opportunities and resources-which might include the provision of both digital and traditional interventions-to address individual needs and interests. We present a case example of how aspects of this model are being applied to increase reach, engagement and outcomes for individuals who complete a national eating disorders screen, and are likely to have an eating disorder but who are not in treatment. We then describe how this model can apply to post-traumatic stress (PTS) and conclude with a discussion of limitations and issues with the model.
Methods: The National Eating Disorders Association (NEDA) provides online screening for eating disorders.
Results: From February 2017 through March 2018, over 200,000 individuals completed the NEDA screen. Of these, 96% screened positive or at risk for an eating disorder, and most of those who screened positive for a clinical/subclinical eating disorder were not currently in treatment. Less than 10% engaged in self-help or guided self-help online digital program, or expressed interest in calling a helpline for referral to treatment.
Conclusions: A systematic digital approach to implementation and dissemination has the potential to increase the number of individuals who benefit from interventions in defined populations. Uptake rates need to be improved
The Rest-Frame Optical Spectrum of MS 1512-cB58
Moderate resolution, near-IR spectroscopy of MS1512-cB58 is presented,
obtained during commissioning of the the Near IR Spectrometer (NIRSPEC) on the
Keck II telescope. The strong lensing of this z=2.72 galaxy by the foreground
cluster MS1512+36 makes it the best candidate for detailed study of the
rest-frame optical properties of Lyman Break Galaxies.
A redshift of z=2.7290+/-0.0007 is inferred from the emission lines, in
contrast to the z=2.7233 calculated from UV observations of interstellar
absorption lines. Using the Balmer line ratios, we find an extinction of
E(B-V)=0.27. Using the line strengths, we infer an SFR=620+/-18 Msun/yr
(H_0=75, q_0=0.1, Lambda =0), a factor of 2 higher than that measured from
narrow-band imaging observations of the galaxy, but a factor of almost 4 lower
than the SFR inferred from the UV continuum luminosity. The width of the Balmer
lines yields a mass of M_vir=1.2x10^10 Msun. We find that the oxygen abundance
is 1/3 solar, in good agreement with other estimates of the metallicity.
However, we infer a high nitrogen abundance, which may argue for the presence
of an older stellar population.Comment: 14 pages, including 3 figures. Accepted for publication in ApJ
Letter
Aptamer conjugated silver nanoparticles for the detection of interleukin 6
The controlled assembly of plasmonic nanoparticles by a molecular binding event has emerged as a simple yet sensitive methodology for protein detection. Metallic nanoparticles (NPs) coated with functionalized aptamers can be utilized as biosensors by monitoring changes in particle optical properties, such as the LSPR shift and enhancement of the SERS spectra, in the presence of a target protein. Herein we test this method using two modified aptamers selected for the protein biomarker interleukin 6, an indicator of the dengue fever virus and other diseases including certain types of cancers, diabetes, and even arthritis. IL6 works by inducing an immunological response within the body that can be either anti-inflammatory or pro-inflammatory. The results show that the average hydrodynamic diameter of the NPs as measured by Dynamic Light Scattering was âŒ42 nm. After conjugation of the aptamers, the peak absorbance of the AgNPs shifted from 404 to 408 nm indicating a surface modification of the NPs due to the presence of the aptamer. Lastly, preliminary results were obtained showing an increase in SERS intensity occurs when the IL-6 protein was introduced to the conjugate solution but the assay will still need to be optimized in order for it to be able to monitor varying concentration changes within and across the desired range
J-Band Infrared Spectroscopy of a Sample of Brown Dwarfs Using Nirspec on Keck II
Near-infrared spectroscopic observations of a sample of very cool, low-mass
objects are presented with higher spectral resolution than in any previous
studies. Six of the objects are L-dwarfs, ranging in spectral class from L2 to
L8/9, and the seventh is a methane or T-dwarf. These new observations were
obtained during commissioning of NIRSPEC, the first high-resolution
near-infrared cryogenic spectrograph for the Keck II 10-meter telescope on
Mauna Kea, Hawaii. Spectra with a resolving power of R=2500 from 1.135 to 1.360
microns (approximately J-band) are presented for each source. At this
resolution, a rich spectral structure is revealed, much of which is due to
blending of unresolved molecular transitions. Strong lines due to neutral
potassium (K I), and bands due to iron hydride (FeH) and steam (H2O) change
significantly throughout the L sequence. Iron hydride disappears between L5 and
L8, the steam bands deepen and the K I lines gradually become weaker but wider
due to pressure broadening. An unidentified feature occurs at 1.22 microns
which has a temperature dependence like FeH but has no counterpart in the
available FeH opacity data. Because these objects are 3-6 magnitudes brighter
in the near-infrared compared to the I-band, spectral classification is
efficient. One of the objects studied (2MASSW J1523+3014) is the coolest
L-dwarf discovered so far by the 2-Micron All-Sky Survey (2MASS), but its
spectrum is still significantly different from the methane-dominated objects
such as Gl229B or SDSS 1624+0029.Comment: New paper, Latex format, 2 figures, accepted to ApJ Letter
Development of a very low-noise cryogenic pre-amplifier for large-area SiPM devices
Silicon Photomultipliers (SiPMs) are an excellent candidate for the
development of large-area light sensors. Large SiPM-based detectors require
low-noise pre-amplifiers to maximize the signal coupling between the sensor and
the readout electronics. This article reports on the development of a low-noise
transimpedance amplifier sensitive to single-photon signals at cryogenic
temperature. The amplifier is used to readout a 1 cm SiPM with a signal
to noise ratio in excess of 40
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