326 research outputs found
Ecophysiological responses of four boreal tree species to soil nitrogen supply
The ecophysiological responses of four boreal tree species, trembling aspen
(Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.S.P.), white spruce
(Picea glauca (Moench) Voss), and jack pine (Pinus banksiana Lamb.) were examined at
six different levels (from 25 to 775 ppm) of soil nitrogen (N). At the 50th and 100th day of
treatment, two-year-old conifer seedlings and six-month-old trembling aspen seedlings were
measured for gas exchange, foliar N concentration, growth and biomass allocation traits.
The gas exchange and resource use efficiency responses varied with species. The
additional N input had no significant effect on photosynthesis (see document) and positive
effect on transpiration (E, mmol/m2/s), and beyond 175 ppm N treatment it produced
negative effect on whole seedling photosynthetic capacity (see document) in trembling
aspen. A, E and At in conifers responded negatively to N treatment, except for a brief
positive response from 25 to 125 ppm N in jack pine. PSII
revealed relevant relationship
with A but only for jack pine and white spruce. We found explicit positive response of
foliar N concentration and negative response of PNUE to increasing soil N availability.
However, the trends of PWUE between species varied across six N treatments and possibly
due to luxury consumption. The PWUE was positively correlated with soil N supply in only
white spruce and was negatively correlated in other species. The sufficient soil N
availability for optimum gas exchange and nutritional status were at 75 ppm N for black
spruce and at 125 for the other three species.
Overall, the growth response of aspen to N was more pronounced than that of
conifers due to its fast growing nature. Significant growth response of aspen occurred
between the 75 to 175 ppm N treatments. Substantial growth reduction occurred when
aspen seedlings were induced to excessively high soil N concentrations (375 and 775 ppm),
specifically due to the vulnerability of these seedlings to pest damages. This is also related
to the significant increase in foliar N concentration at these N treatments. Greatest growth
was achieved at 25 ppm N addition rate in black spruce and jack pine, and most notables at
125 ppm N in white spruce. However, these N levels are not conclusive when optimum soil
N concentration(s) for gas exchange parameters, particularly for At, in these seedlings are
taken into consideration. Nonetheless, at highest soil N supply (375 and 775 ppm), the
growth of conifer seedlings was not as adversely affected as that of aspen seedlings. Our
results also proved strong significance of N availability on biomass allocation between root
and shoot components and height growth in all species. Root production was significantly suppressed as soil N availability increased in the conifers. The opposite was found in aspen.
In conifers, the proportions of total seedling biomass allocated to roots (or the root-toshoot
ratio, R/S), at all N treatments, were highest in white spruce, followed by black
spruce then jack pine. The R/S ratio in aspen was comparable with, but followed an
opposite pattern to, white spruce. The stem and foliage productions in all studied species
showed negligible positive response to increasing soil N treatments. However, with the
exception of aspen, the order of the species allocating highest to lowest portions of its total
biomass to the foliage followed the exact opposite pattern as that of root allocation
percentage. Aspen showed lesser biomass allocation to the foliage than conifers. However,
it allocated highest percentages of total seedling biomass to the stem, at all N treatments,
followed in sequential order by black spruce, white spruce and jack pine.
When all ecophysiological parameters are considered, our results indicated that low
soil N availability, such as that at 25 ppm, does not adversely affect the boreal seedling
growth and survival as much as it does at excessively high soil N availability (e.g., 375 and
775 ppm). Within the sufficient N regimes (i.e., 75 - 175 ppm), the most suitable soil N
concentration for black spruce is at 75 ppm and at 125 ppm for other species
Toward an understanding of tourists’ authentic heritage experiences: Evidence from Hong Kong
Authenticity in tourism has been a topic of discussion since the 1960s, but the concept is still to be fully developed. This study focuses on tourists’ perceptions of authenticity, and in particular how they evaluate authentic heritage experiences. The appearance and physical settings of attractions were found to be the initial and most important indicators of authentic or inauthentic experiences. Other criteria for assessing the authenticity of heritage experiences include the presence of local culture and customs, constructed elements, commodification, and atmosphere
Virulence of Mycobacterium tuberculosis Clinical Isolates Is Associated With Sputum Pre-treatment Bacterial Load, Lineage, Survival in Macrophages, and Cytokine Response
It is uncertain whether differences in Mycobacterium tuberculosis (Mtb) virulence defined in vitro influence clinical tuberculosis pathogenesis, transmission, and mortality. We primarily used a macrophage lysis model to characterize the virulence of Mtb isolates collected from 153 Vietnamese adults with pulmonary tuberculosis. The virulence phenotypes were then investigated for their relationship with sputum bacterial load, bacterial lineages, bacterial growth, and cytokine responses in macrophages. Over 6 days of infection, 34 isolates (22.2%) showed low virulence (< 5% macrophages lysed), 46 isolates (30.1%) showed high virulence (≥90% lysis of macrophages), and 73 isolates (47.7%) were of intermediate virulence (5–90% macrophages lysed). Highly virulent isolates were associated with an increased bacterial load in patients' sputum before anti-tuberculosis therapy (P = 0.02). Isolate-dependent virulence phenotype was consistent in both THP-1 and human monocyte-derived macrophages. High virulence isolates survived better and replicated in macrophages one hundred fold faster than those with low virulence. Macrophages infected with high virulence isolates produced lower concentrations of TNF-α and IL-6 (P = 0.002 and 0.0005, respectively), but higher concentration of IL-1β (P = 5.1 × 10−5) compared to those infected with low virulence isolates. High virulence was strongly associated with East Asian/Beijing lineage [P = 0.002, Odd ratio (OR) = 4.32, 95% confident intervals (CI) 1.68–11.13]. The association between virulence phenotypes, bacterial growth, and proinflammatory cytokines in macrophages suggest the suppression of certain proinflammatory cytokines (TNF-α and IL-6) but not IL-1β allows better intracellular survival of highly virulent Mtb. This could result in rapid macrophage lysis and higher bacterial load in sputum of patients infected with high virulence isolates, which may contribute to the pathogenesis and success of the Beijing lineage
Optical Propagation and Communication
Contains reports on four research projects.National Science Foundation (Grant ECS81-20637)U.S. Navy - Office of Naval Research (Contract N00014-81-K-0662)U.S. Army Research Office - Durham (Contract DAAG29-80-K-0022)U.S. Navy - Office of Naval Research (Contract N00014-80-C-0941
Optical Propagation and Communication
Contains summary of research and reports on four research projects.National Science Foundation (Grant ECS81-20637)U.S. Navy - Office of Naval Research (Contract N00014-81-K-0662)Maryland Procurement Office (Contract MDA904-84-C-6037)U.S. Army Research Office - Durham (Contract DAAG29-80-K-0022)U.S. Army Research Office - Durham (Contract DAAG29-84-K-0095)U.S. Navy - Office of Naval Research (Contract N00014-80-C-0941
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Unusual shock-excited oh maser emission in a young Planetary Nebula
© 2016. The American Astronomical Society. All rights reserved. We report on OH maser emission toward G336.644-0.695 (IRAS 16333-4807), which is a H2O maser-emitting Planetary Nebula (PN). We have detected 1612, 1667, and 1720 MHz OH masers at two epochs using the Australia Telescope Compact Array, hereby confirming it as the seventh known case of an OH-maser-emitting PN. This is only the second known PN showing 1720 MHz OH masers after K 3-35 and the only evolved stellar object with 1720 MHz OH masers as the strongest transition. This PN is one of a group of very young PNe. The 1612 MHz and 1667 MHz masers are at a similar velocity to the 22 GHz H2O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s-1). We also detect Zeeman splitting in the 1720 MHz transition at two epochs (with field strengths of ~2 to ~10 mG), which suggests the OH emission at 1720 MHz is formed in a magnetized environment. These 1720 MHz OH masers may trace short-lived equatorial ejections during the formation of the PN
Accurate OH maser positions from the SPLASH pilot region
We report on high spatial resolution observations, using the Australia Telescope Compact Array (ATCA), of ground-state OH masers. These observations were carried out toward 196 pointing centers previously identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) pilot region, between Galactic longitudes of 334 and 344 and Galactic latitudes of -2 and +2. Supplementing our data with data from the MAGMO (Mapping the Galactic Magnetic field through OH masers) survey, we find maser emission toward 175 of the 196 target fields. We conclude that about half of the 21 nondetections were due to intrinsic variability. Due to the superior sensitivity of the followup ATCA observations, and the ability to resolve nearby sources into separate sites, we have identified 215 OH maser sites toward the 175 fields with detections. Among these 215 OH maser sites, 111 are new detections. After comparing the positions of these 215 maser sites to the literature, we identify 122 (57%) sites associated with evolved stars (one of which is a planetary nebula), 64 (30%) with star formation, two sites with supernova remnants, and 27 (13%) of unknown origin. The infrared colors of evolved star sites with symmetric maser profiles tend to be redder than those of evolved star sites with asymmetric maser profiles, which may indicate that symmetric sources are generally at an earlier evolutionary stage. © 2016. The American Astronomical Society. All rights reserved
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in
Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference
Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images
Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images
of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL
maps are derived through computational staining using a convolutional neural network trained to
classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and
correlation with overall survival. TIL map structural patterns were grouped using standard
histopathological parameters. These patterns are enriched in particular T cell subpopulations
derived from molecular measures. TIL densities and spatial structure were differentially enriched
among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial
infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic
patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for
the TCGA image archives with insights into the tumor-immune microenvironment
- …