1,033 research outputs found
Do supplemental list frames for subpopulations increase subpopulation sampling efficiency? Evidence from the National Household Food Acquisition and Purchase Survey
Multiple-frame sampling has been regarded as a device for increasing efficiency in identifying small subpopulations. However, there has
been a lack of empirical evidence in supporting the efficiency of the multiple-frame approach and in guiding best practices. The current
study focuses on a special scenario in which two frames were used to recruit sample members. Using paradata from the U.S. National
Household Food Acquisition and Purchase Survey (FoodAPS), the current analysis focuses on recruiting households that received
Supplementary Nutrition Assistance Program (SNAP) as a sub-goal of the survey sampling. SNAP households account for around one-fifth
of the general U.S. population, compared to a survey goal of 30 percent of responding households. Our findings were consistent with
theoretical expectations. Having and using additional SNAP list frames improved the efficiency of identifying SNAP households as opposed
to screening a general address-based sample frame. This efficiency remained even as the SNAP list frames aged
Hot summers in the Western United States during the Late Cretaceous and Early Cenozoic
Understanding how seasonal temperatures on land respond to global greenhouse climate conditions is important for
predicting effects of climate change on ecosystem structure, agriculture and distributions of natural resources. Fossil floral
and faunal assemblages suggest winter temperatures in middle and high latitude continental interiors during the Cretaceous
and early Cenozoic were at or above freezing, whereas terrestrial summer temperature estimates are uncertain.
Carbonate clumped isotope (Δ_(47)) temperature estimates from lacustrine and paleosol carbonates appear to be generally
biased toward summer temperatures in middle and high latitudes. Though problematic for reconstructing mean annual
temperature (MAT), this bias presents an opportunity to reconstruct terrestrial summer temperatures and, through
comparison with paleobotanical data, estimate past terrestrial seasonality
Quasinormal Modes in three-dimensional time-dependent Anti-de Sitter spacetime
The massless scalar wave propagation in the time-dependent BTZ black hole
background has been studied. It is shown that in the quasi-normal ringing both
the decay and oscillation time-scales are modified in the time-dependent
background.Comment: 8 pages and 7 figure
Quantum corrections to critical phenomena in gravitational collapse
We investigate conformally coupled quantum matter fields on spherically
symmetric, continuously self-similar backgrounds. By exploiting the symmetry
associated with the self-similarity the general structure of the renormalized
quantum stress-energy tensor can be derived. As an immediate application we
consider a combination of classical, and quantum perturbations about exactly
critical collapse. Generalizing the standard argument which explains the
scaling law for black hole mass, , we
demonstrate the existence of a quantum mass gap when the classical critical
exponent satisfies . When our argument is
inconclusive; the semi-classical approximation breaks down in the spacetime
region of interest.Comment: RevTeX, 6 pages, 3 figures included using psfi
Return of the quantum cosmic censor
The influential theorems of Hawking and Penrose demonstrate that spacetime
singularities are ubiquitous features of general relativity, Einstein's theory
of gravity. The utility of classical general relativity in describing
gravitational phenomena is maintained by the cosmic censorship principle. This
conjecture, whose validity is still one of the most important open questions in
general relativity, asserts that the undesirable spacetime singularities are
always hidden inside of black holes. In this Letter we reanalyze extreme
situations which have been considered as counterexamples to the cosmic
censorship hypothesis. In particular, we consider the absorption of fermion
particles by a spinning black hole. Ignoring quantum effects may lead one to
conclude that an incident fermion wave may over spin the black hole, thereby
exposing its inner singularity to distant observers. However, we show that when
quantum effects are properly taken into account, the integrity of the
black-hole event horizon is irrefutable. This observation suggests that the
cosmic censorship principle is intrinsically a quantum phenomena.Comment: 5 page
Internal Structure of Einstein-Yang-Mills Black Holes
It is shown that a generic black hole solution of the SU(2)
Einstein-Yang-Mills equations develops a new type of an infinitely oscillating
behavior near the singularity. Only for certain discrete values of the event
horizon radius exceptional solutions exist, possessing an inner structure of
the Schwarzschild or Reissner-Nordstrom type.Comment: 4.5 LaTeX pages, 8 eps figures, uses RevTeX, boxedeps.tex. 4 more
typos fixed, a footnote adde
The Central Singularity in Spherical Collapse
The gravitational strength of the central singularity in spherically
symmetric space-times is investigated. Necessary conditions for the singularity
to be gravitationally weak are derived and it is shown that these are violated
in a wide variety of circumstances. These conditions allow conclusions to be
drawn about the nature of the singularity without having to integrate the
geodesic equations. In particular, any geodesic with a non-zero amount of
angular momentum which impinges on the singularity terminates in a strong
curvature singularity.Comment: 17 pages; revised and corrected with improved result
Multiplex immunofluorescence to measure dynamic changes in tumor-infiltrating lymphocytes and PD-L1 in early-stage breast cancer.
BACKGROUND: The H&E stromal tumor-infiltrating lymphocyte (sTIL) score and programmed death ligand 1 (PD-L1) SP142 immunohistochemistry assay are prognostic and predictive in early-stage breast cancer, but are operator-dependent and may have insufficient precision to characterize dynamic changes in sTILs/PD-L1 in the context of clinical research. We illustrate how multiplex immunofluorescence (mIF) combined with statistical modeling can be used to precisely estimate dynamic changes in sTIL score, PD-L1 expression, and other immune variables from a single paraffin-embedded slide, thus enabling comprehensive characterization of activity of novel immunotherapy agents.
METHODS: Serial tissue was obtained from a recent clinical trial evaluating loco-regional cytokine delivery as a strategy to promote immune cell infiltration and activation in breast tumors. Pre-treatment biopsies and post-treatment tumor resections were analyzed by mIF (PerkinElmer Vectra) using an antibody panel that characterized tumor cells (cytokeratin-positive), immune cells (CD3, CD8, CD163, FoxP3), and PD-L1 expression. mIF estimates of sTIL score and PD-L1 expression were compared to the H&E/SP142 clinical assays. Hierarchical linear modeling was utilized to compare pre- and post-treatment immune cell expression, account for correlation of time-dependent measurement, variation across high-powered magnification views within each subject, and variation between subjects. Simulation methods (Monte Carlo, bootstrapping) were used to evaluate the impact of model and tissue sample size on statistical power.
RESULTS: mIF estimates of sTIL and PD-L1 expression were strongly correlated with their respective clinical assays (p \u3c .001). Hierarchical linear modeling resulted in more precise estimates of treatment-related increases in sTIL, PD-L1, and other metrics such as CD8+ tumor nest infiltration. Statistical precision was dependent on adequate tissue sampling, with at least 15 high-powered fields recommended per specimen. Compared to conventional t-testing of means, hierarchical linear modeling was associated with substantial reductions in enrollment size required (n = 25➔n = 13) to detect the observed increases in sTIL/PD-L1.
CONCLUSION: mIF is useful for quantifying treatment-related dynamic changes in sTILs/PD-L1 and is concordant with clinical assays, but with greater precision. Hierarchical linear modeling can mitigate the effects of intratumoral heterogeneity on immune cell count estimations, allowing for more efficient detection of treatment-related pharmocodynamic effects in the context of clinical trials.
TRIAL REGISTRATION: NCT02950259
Characterizing degradation of palm swamp peatlands from space and on the ground: an exploratory study in the Peruvian Amazon
Peru has the fourth largest area of peatlands in the Tropics. Its most representative land cover on peat is a Mauritia flexuosa dominated palm swamp (thereafter called dense PS), which has been under human pressure over decades due to the high demand for the M. flexuosa fruit often collected by cutting down the entire palm. Degradation of these carbon dense forests can substantially affect emissions of greenhouse gases and contribute to climate change. The first objective of this research was to assess the impact of dense PS degradation on forest structure and biomass carbon stocks. The second one was to explore the potential of mapping the distribution of dense PS with different degradation levels using remote sensing data and methods. Biomass stocks were measured in 0.25 ha plots established in areas of dense PS with low (n = 2 plots), medium (n = 2) and high degradation (n = 4). We combined field and remote sensing data from the satellites Landsat TM and ALOS/PALSAR to discriminate between areas typifying dense PS with low, medium and high degradation and terra firme, restinga and mixed PS (not M. flexuosa dominated) forests. For this we used a Random Forest machine learning classification algorithm. Results suggest a shift in forest composition from palm to woody tree dominated forest following degradation. We also found that human intervention in dense PS translates into significant reductions in tree carbon stocks with initial (above and below-ground) biomass stocks (135.4 ± 4.8 Mg C ha−1) decreased by 11 and 17% following medium and high degradation. The remote sensing analysis indicates a high separability between dense PS with low degradation from all other categories. Dense PS with medium and high degradation were highly separable from most categories except for restinga forests and mixed PS. Results also showed that data from both active and passive remote sensing sensors are important for the mapping of dense PS degradation. Overall land cover classification accuracy was high (91%). Results from this pilot analysis are encouraging to further explore the use of remote sensing data and methods for monitoring dense PS degradation at broader scales in the Peruvian Amazon. Providing precise estimates on the spatial extent of dense PS degradation and on biomass and peat derived emissions is required for assessing national emissions from forest degradation in Peru and is essential for supporting initiatives aiming at reducing degradation activities
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