2,861 research outputs found
Noncytotoxic Roles of Granzymes in Health and Disease
Granzymes are serine proteases previously believed to play exclusive and somewhat redundant roles in lymphocyte-mediated target cell death. However, recent studies have challenged this paradigm. Distinct substrate profiles and functions have since emerged for each granzyme while their dysregulated proteolytic activities have been linked to diverse pathologies
Root oxygen mitigates methane fluxes in tropical peatlands
Tropical peatlands are a globally important source of methane, a potent greenhouse gas. Vegetation is critical in regulating fluxes, providing a conduit for emissions and regular carbon inputs. However, plant roots also release oxygen, which might mitigate methane efflux through oxidation prior to emission from the peat surface. Here we show, using in situ mesocosms, that root exclusion can reduce methane fluxes by a maximum of 92% depending on species, likely driven by the significant decrease in root inputs of oxygen and changes in the balance of methane transport pathways. Methanotroph abundance decreased with reduced oxygen input, demonstrating a likely mechanism for the observed response. These first methane oxidation estimates for a tropical peatland demonstrate that although plants provide an important pathway for methane loss, this can be balanced by the influence of root oxygen inputs that mitigate peat surface methane emissions
Optoelectronic analysis of multijunction wire array solar cells
Wire arrays have demonstrated promising photovoltaic performance as single junction solar cells and are well suited to defect mitigation in heteroepitaxy. These attributes can combine in tandem wire array solar cells, potentially leading to high efficiencies. Here, we demonstrate initial growths of GaAs on Si_(0.9)Ge_(0.1) structures and investigate III-V on Si_(1-x)Ge_x device design with an analytical model and optoelectronic simulations. We consider Si_(0.1)Ge_(0.9) wires coated with a GaAs_(0.9)P_(0.1) shell in three different geometries: conformal, hemispherical, and spherical. The analytical model indicates that efficiencies approaching 34% are achievable with high quality materials. Full field electromagnetic simulations serve to elucidate the optical loss mechanisms and demonstrate light guiding into the wire core. Simulated current-voltage curves under solar illumination reveal the impact of a varying GaAs_(0.9)P_(0.1) minority carrier lifetime. Finally, defective regions at the hetero-interface are shown to have a negligible effect on device performance if highly doped so as to serve as a back surface field. Overall, the growths and the model demonstrate the feasibility of the proposed geometries and can be used to guide tandem wire array solar cell designs
Electroconvulsive Therapy Response in Major Depressive Disorder: a Pilot Functional Network Connectivity Resting State FMRI Investigation
Major depressive disorder (MDD) is associated with increased functional connectivity in specific neural networks. Electroconvulsive therapy (ECT), the gold-standard treat- ment for acute, treatment-resistant MDD, but temporal dependencies between networks associated with ECT response have yet to be investigated. In the present longitudinal, case–control investigation, we used independent component analysis to identify distinct networks of brain regions with temporally coherent hemodynamic signal change and func- tional network connectivity (FNC) to assess component time course correlations across these networks. MDD subjects completed imaging and clinical assessments immediately prior to the ECT series and a minimum of 5 days after the last ECT treatment. We focused our analysis on four networks affected in MDD: the subcallosal cingulate gyrus, default mode, dorsal lateral prefrontal cortex, and dorsal medial prefrontal cortex (DMPFC). In an older sample of ECT subjects (n = 12) with MDD, remission associated with the ECT series reverses the relationship from negative to positive between the posterior default mode (p_DM) and two other networks: the DMPFC and left dorsal lateral prefrontal cortex (l_DLPFC). Relative to demographically healthy subjects (n = 12), the FNC between the p_DM areas and the DMPFC normalizes with ECT response. The FNC changes following treatment did not correlate with symptom improvement; however, a direct comparison between ECT remitters and non-remitters showed the pattern of increased FNC between the p_DM and l_DLPFC following ECT to be specific to those who responded to the treat- ment.The differences between ECT remitters and non-remitters suggest that this increased FNC between p_DM areas and the left dorsolateral prefrontal cortex is a neural correlate and potential biomarker of recovery from a depressed episode
A Sm(II)-mediated cascade approach to Dibenzoindolo[3,2-b]carbazoles:synthesis and evaluation
Previously unstudied dibenzoindolo[3,2-b]carbazoles have been prepared by two-directional, phase tag-assisted synthesis utilizing a connective-Pummerer cyclization and a SmI2-mediated tag cleavage-cyclization cascade. The use of a phase tag allows us to exploit unstable intermediates that would otherwise need to be avoided. The novel materials were characterized by X-ray, cyclic voltammetry, UV-vis spectroscopy, TGA, and DSC. Preliminary studies on the performance of OFET devices are also described
The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for Its Imaged Companions
HR 8799 is an hF0 mA5 gamma Doradus, lambda Bootis, Vega-type star best known
for hosting four directly imaged candidate planetary companions. Using the
CHARA Array interferometer, we measure HR 8799's limb-darkened angular diameter
to be 0.342 +/- 0.008 mas; this is the smallest interferometrically measured
stellar diameter to date, with an error of only 2%. By combining our
measurement with the star's parallax and photometry from the literature, we
greatly improve upon previous estimates of its fundamental parameters,
including stellar radius (1.44 +/- 0.06 R_Sun), effective temperature (7193 +/-
87 K, consistent with F0), luminosity (5.05 +/- 0.29 L_Sun), and the extent of
the habitable zone (1.62 AU to 3.32 AU). These improved stellar properties
permit much more precise comparisons with stellar evolutionary models, from
which a mass and age can be determined, once the metallicity of the star is
known. Considering the observational properties of other lambda Bootis stars
and the indirect evidence for youth of HR 8799, we argue that the internal
abundance, and what we refer to as the effective abundance, is most likely
near-solar. Finally, using the Yonsei-Yale evolutionary models with uniformly
scaled solar-like abundances, we estimate HR 8799's mass and age considering
two possibilities: 1.516 +0.038/-0.024 M_Sun and 33 +7/-13 Myr if the star is
contracting toward the zero age main-sequence or 1.513 +0.023/-0.024 M_Sun and
90 +381/-50 Myr if it is expanding from it. This improved estimate of HR 8799's
age with realistic uncertainties provides the best constraints to date on the
masses of its orbiting companions, and strongly suggests they are indeed
planets. They nevertheless all appear to orbit well outside the habitable zone
of this young star.Comment: Accepted for publication in ApJ; 37 pages, 6 tables, 13 figure
Spitzer observations of the Massive star forming complex S254-S258: structure and evolution
We present Spitzer-IRAC, NOAO 2.1meter-Flamingos, Keck-NIRC, and
FCRAO-SEQUOIA observations of the massive star forming complex S254-S258,
covering an area of 25x20 arc-minutes. Using a combination of the IRAC and NIR
data, we identify and classify the young stellar objects (YSO) in the complex.
We detect 510 sources with near or mid IR-excess, and we classify 87 Class I,
and 165 Class II sources. The YSO are found in clusters surrounded by isolated
YSO in a low-density distributed population. The ratio of clustered to total
YSO is 0.8. We identify six new clusters in the complex. One of them,
G192.63-00, is located around the ionizing star of the HII region S255. We
hypothesize that the ionizing star of S255 was formed in this cluster. We also
detect a southern component of the cluster in HII region S256. The cluster
G192.54-0.15, located inside HII region S254 has a VLSR of 17 km/s with respect
to the main cloud, and we conclude that it is located in the background of the
complex. The structure of the molecular cloud is examined using 12CO and 13CO,
as well as a near-IR extinction map. The main body of the molecular cloud has
VLSR between 5 and 9 km/s. The arc-shaped structure of the molecular cloud,
following the border of the HII regions, and the high column density in the
border of the HII regions support the idea that the material has been swept up
by the expansion of the HII regions.Comment: Accepted for publication in The Astrophysical Journa
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