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Trade-offs in motivating volunteer effort: Experimental evidence on voluntary contributions to science.
Digitization has facilitated the proliferation of crowd science by lowering the cost of finding individuals with the willingness to participate in science without pay. However, the factors that influence participation and the outcomes of voluntary participation are unclear. We report two findings from a field experiment on the world's largest crowd science platform that tests how voluntary contributions to science are affected by providing clarifying information on either the desired outcome of a scientific task or the labor requirements for completing the task. First, there is significant heterogeneity in the motivations and ability of contributors to crowd science. Second, both of the information interventions lead to significant decreases in the quantity and increases in the quality of contributions. Combined, our findings are consistent with the information interventions improving match quality between the task and the volunteer. Our findings suggest that science can be democratized by engaging individuals with varying skill levels and motivations with small changes in the information provided to participants
Very Low Energy Supernovae: Light Curves and Spectra of Shock Breakout
The brief transient emitted as a shock wave erupts through the surface of a
presupernova star carries information about the stellar radius and explosion
energy. Here the CASTRO code, which treats radiation transport using multigroup
flux-limited diffusion, is used to simulate the light curves and spectra of
shock breakout in very low-energy supernovae (VLE SNe), explosions in giant
stars with final kinetic energy much less than 10 erg. VLE SNe light
curves, computed here with the KEPLER code, are distinctively faint, red, and
long-lived, making them challenging to find with transient surveys. The
accompanying shock breakouts are brighter, though briefer, and potentially
easier to detect. Previous analytic work provides general guidance, but
numerical simulations are challenging due to the range of conditions and lack
of equilibration between color and effective temperatures. We consider previous
analytic work and extend discussions of color temperature and opacity to the
lower energy range explored by these events. Since this is the first
application of the CASTRO code to shock breakout, test simulations of normal
energy shock breakout of SN1987A are carried out and compared with the
literature. A set of breakout light curves and spectra are then calculated for
VLE SNe with final kinetic energies in the range ergs for
red supergiants with main sequence masses 15 Msun and 25 Msun. The importance
of uncertainties in stellar atmosphere model, opacity, and ambient medium is
discussed, as are observational prospects with current and forthcoming
missions.Comment: 19 pages; submitted to Astrophysical Journa
The Number of Seymour Vertices in Random Tournaments and Digraphs
Seymour's distance two conjecture states that in any digraph there exists a
vertex (a "Seymour vertex") that has at least as many neighbors at distance two
as it does at distance one. We explore the validity of probabilistic statements
along lines suggested by Seymour's conjecture, proving that almost surely there
are a "large" number of Seymour vertices in random tournaments and "even more"
in general random digraphs.Comment: 14 page
The Total Acquisition Number of the Randomly Weighted Path
There exists a significant body of work on determining the acquisition number
of various graphs when the vertices of those graphs are each initially
assigned a unit weight. We determine properties of the acquisition number of
the path, star, complete, complete bipartite, cycle, and wheel graphs for
variations on this initial weighting scheme, with the majority of our work
focusing on the expected acquisition number of randomly weighted graphs. In
particular, we bound the expected acquisition number of the
-path when distinguishable "units" of integral weight, or chips, are
randomly distributed across its vertices between and . With
computer support, we improve it by showing that lies between
and . We then use subadditivity to show that the limiting
ratio exists, and simulations reveal more exactly what the
limiting value equals. The Hoeffding-Azuma inequality is used to prove that the
acquisition number is tightly concentrated around its expected value.
Additionally, in a different context, we offer a non-optimal acquisition
protocol algorithm for the randomly weighted path and exactly compute the
expected size of the resultant residual set.Comment: 19 page
Compressed Distributed Gradient Descent: Communication-Efficient Consensus over Networks
Network consensus optimization has received increasing attention in recent
years and has found important applications in many scientific and engineering
fields. To solve network consensus optimization problems, one of the most
well-known approaches is the distributed gradient descent method (DGD).
However, in networks with slow communication rates, DGD's performance is
unsatisfactory for solving high-dimensional network consensus problems due to
the communication bottleneck. This motivates us to design a
communication-efficient DGD-type algorithm based on compressed information
exchanges. Our contributions in this paper are three-fold: i) We develop a
communication-efficient algorithm called amplified-differential compression DGD
(ADC-DGD) and show that it converges under {\em any} unbiased compression
operator; ii) We rigorously prove the convergence performances of ADC-DGD and
show that they match with those of DGD without compression; iii) We reveal an
interesting phase transition phenomenon in the convergence speed of ADC-DGD.
Collectively, our findings advance the state-of-the-art of network consensus
optimization theory.Comment: 11 pages, 11 figures, IEEE INFOCOM 201
JeffHEALTH: Helping East Africa Link to Health
JeffHEALTH-Helping East Africa Link to Health is a student-run organization at Thomas Jefferson University dedicated to improving basic medical education and quality of life in Rwanda, which was devastated in 1994 by civil war and genocide. Working in partnership with the Rwanda Village Concept Project, a student organization at the National University of Rwanda, JeffHEALTH seeks to implement sustainable health initiatives in our partner villages. Graduate students from Thomas Jefferson University travel to Rwanda where we taught Community Health Workers from the Villages of Akarambi and Ruli the following topics: Nutrition and Vitamin Deficiencies, Family Planning, Prenatal care, HIV, Sexually Transmitted Illnesses and Hepatitis, Breast and Cervical Cancer, Diabetes, and Fistulas. We also taught two programs to children of the villages (Oral Hygiene and Soil Transmitted Helminths) and talked with young adults about Circumcision and HIV Prevention and Sex Education.https://jdc.jefferson.edu/cwicposters/1018/thumbnail.jp
THE ROLE OF ADAPTOR PROTEIN GADS IN CD8+ T CELL-MEDIATED IMMUNITY
CD8+ T cells are the branch of the adaptive immune system responsible for recognizing and killing tumor cells or cells infected with intracellular pathogens, such as Listeria monocytogenes (LM). However, when CD8+ T cells target our own tissues, they can cause autoimmune diseases, such as type I diabetes, rheumatoid arthritis. For CD8+ T cells to fulfill these functions, the T cell receptors (TCRs) on CD8+ T cells must recognize pathogens or antigens presented on the surface of target cells. TCR ligation triggers multiple signaling pathways that lead to the activation and proliferation of CD8+ T cells. The goal of our research is to define the TCR-proximal signaling events that regulate CD8+ T cell-mediated immunity. To accomplish this goal, we are focusing on an adaptor protein Gads, which is critical for optimal TCR-mediated calcium mobilization. We reported the first analysis of the function of Gads in peripheral naïve CD8+ T cells. To examine the function of Gads in CD8+ T cell mediated immune responses, we crossed Gads-/- mice with mice expressing an MHC class I-restricted transgenic TCR recognizing ovalbumin (OVA). The transgenic mice are called ovalbumin-specific T cell receptor-major histocompatibility complex class I restricted (OT-I) mice. We investigated the effect of Gads on the proliferation of CD8+ T cells following stimulation with peptide antigen in vivo and in vitro. We stimulated splenocytes from Gads+/+ OT-I and Gads-/- OT-I mice with the peptide agonist. The experiments revealed that Gads is required for optimal proliferation of CD8+ T cells. The regulation of Gads is most evident at the early time points of proliferation. Then we demonstrated that Gads-/- CD8+ T cells have impaired TCR-mediated exit from G0 phase of the cell cycle. In addition, Gads-/- CD8+ T cells have delayed expression of c-myc and the activation markers CD69 and CD25, upon stimulation with peptide antigen. Next, we investigated how Gads affects CD8+ T cell-mediated immunity in the context of infection with LM. We adoptively transferred naïve CD8+ T cells from Gads+/+ OT-I mice and/or Gads-/- OT-I mice into congenic wild-type hosts. Then the recipient mice were infected with recombinant LM expressing ovalbumin (rLM-OVA). The CD8+ T cells from OT-I mice recognize and respond to the ovalbumin provided by this strain of LM. By using this system, we investigated how Gads regulates the activation of antigen-specific CD8+ T cells as well as the expansion and memory phases of CD8+ T cell-mediated immune responses following infection with rLM-OVA. We also examined the recall response of CD8+ T cells after the secondary encounter with the same pathogen. Our data demonstrated that Gads regulates the expression of activation markers CD69 and CD25 of antigen-specific CD8+ T cells but Gads is not required for the onset of accumulation of antigen-specific CD8+ T cells following infection. However, Gads is critical to sustain the expansion of CD8+ T cell-mediated immune response following infection. Although the differentiation of naïve CD8+ T cells into memory cells is independent of Gads, Gads is required for an optimal recall response. Our data indicating that Gads regulates the initiation of proliferation of CD8+ T cells upon TCR ligation by peptide antigen seemed to contradict with our in vivo infection data showing that Gads is not required for the initiation of expansion of CD8+ T cell population. In order to explain the "discrepancy", we hypothesized that the homotypic interactions among CD8+ T cells compensate for Gads deficiency at the initial stage of accumulation of antigen-specific CD8+ T cells upon infection. Our data indicated that the need for Gads in cell cycle progression of CD8+ T cells when total splenocytes were stimulated could be overcome by stimulating purified CD8+ T cells. These data suggested that the homotypic interactions among CD8+ T cells facilitate the TCR signaling so as to compensate for Gads deficiency in promoting cell cycle entry and proliferation. To conclude, the role of Gads in TCR-mediated activation and proliferation of CD8+ T cells is dependent on the interactions of CD8+ T cells and their partners. Interestingly, if CD8+ T cells interact with non-CD8+ T cells, Gads regulates the kinetics of cell cycle entry; however, if CD8+ T cells interact with other CD8+ T cells, Gads is dispensable for cell cycle entry of CD8+ T cells. Overall, these studies will help us better understand how TCR-proximal signaling regulates the activation of CD8+ T cells
Transciptome Analysis Illuminates the Nature of the Intracellular Interaction in a Vertebrate-Algal Symbiosis
During embryonic development, cells of the green alga Oophila amblystomatis enter cells of the salamander Ambystoma maculatum forming an endosymbiosis. Here, using de novo dual-RNA seq, we compared the host salamander cells that harbored intracellular algae to those without algae and the algae inside the animal cells to those in the egg capsule. This two-by-two-way analysis revealed that intracellular algae exhibit hallmarks of cellular stress and undergo a striking metabolic shift from oxidative metabolism to fermentation. Culturing experiments with the alga showed that host glutamine may be utilized by the algal endosymbiont as a primary nitrogen source. Transcriptional changes in salamander cells suggest an innate immune response to the alga, with potential attenuation of NF-κB, and metabolic alterations indicative of modulation of insulin sensitivity. In stark contrast to its algal endosymbiont, the salamander cells did not exhibit major stress responses, suggesting that the host cell experience is neutral or beneficial
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