6,632 research outputs found
Compact Three Mirror Anastigmat Space Telescope Design using 6.5m Monolithic Primary Mirror
The utilization of a 6.5m monolithic primary mirror in a compact three-mirror
anastigmat (TMA) telescope design offers unprecedented capabilities to
accommodate various next generation science instruments. This design enables
the rapid and efficient development of a large aperture telescope without
segmented mirrors while maintaining a compact overall form factor. With its
exceptional photon collection area and diffraction-limited resolving power, the
TMA design is ideally suited for both the ground and space active/adaptive
optics concepts, which require the capture of natural guide stars within the
field of view for wavefront measurement to correct for misalignments and shape
deformation caused by thermal gradients. The wide field of view requirement is
based on a statistical analysis of bright natural guide stars available during
observation. The primary mirror clear aperture, compactness requirement, and
detector pixel sizes led to the choice of TMA over simpler two-mirror solutions
like Ritchey-Chretien (RC) telescopes, and the TMA design offers superior
diffraction-limited performance across the entire field of view. The standard
conic surfaces applied to all three mirrors (M1, M2, and M3) simplify the
optical fabrication, testing, and alignment process. Additionally, the TMA
design is more tolerant than RC telescopes. Stray light control is critical for
UV science instrumentation, and the field stop and Lyot stop are conveniently
located in the TMA design for this purpose.Comment: Presented at SPIE, Optics+Photonics 2023, Astronomical Optics:
Design, Manufacture, and Test of Space and Ground Systems IV in San Diego,
CA, US
Comparison of characteristics among Korean American male smokers between survey and cessation studies
This study compared characteristics of Korean American men in two studies: a telephone survey with a random sample of Korean American men who reported daily smoking versus a smoking cessation clinical trial with a convenience sample of Korean American men who reported smoking at least 10 cigarettes a day. Guided by the Theory of Planned Behavior (TPB), both studies attempted to explain how much its theoretical variables (attitudes, perceived social norms, and self-efficacy) would explain quit intentions in Korean American men. Participants in the cessation study were less likely to have health insurance coverage (χ2 [2, 271] = 138.31, p = 0.001) than those in the survey study. The cessation group was more likely to smoke in indoor offices (χ2 [1, 231] = 18.09, p = 0.003) and had higher nicotine dependence than the survey group (t269 = 3.32, p = 0.001) but these differences became insignificant when only those who smoked 10 or more cigarettes were compared. Participants in the cessation study had more positive attitudes towards quitting (t267 = 4.99, p \u3c 0.001), stronger perceived social norms favoring quitting (t269 = 5.63, p \u3c 0.001) and greater quit intentions (t268 = 9.86, p \u3c 0.001) at baseline than those in the survey study. Korean American men are more likely to have a quit intention and make a quit attempt when they have more positive and fewer negative attitudes towards quitting and perceive stronger social norms favoring quitting. To motivate Korean American men to quit smoking, clinicians should underscore the immediate health benefits of quitting, promote quitting with cessation aids to reduce perceived risks of quitting in anticipation of withdrawal symptoms, and encourage family members to relate firm anti-smoking messages
Measurement of the Background Activities of a 100Mo-enriched powder sample for AMoRE crystal material using a single high purity germanium detector
The Advanced Molybdenum-based Rare process Experiment (AMoRE) searches for
neutrino-less double-beta (0{\nu}\b{eta}\b{eta}) decay of 100Mo in enriched
molybdate crystals. The AMoRE crystals must have low levels of radioactive
contamination to achieve low background signals with energies near the Q-value
of the 100Mo 0{\nu}\b{eta}\b{eta} decay. To produce low-activity crystals,
radioactive contaminants in the raw materials used to form the crystals must be
controlled and quantified. 100EnrMoO3 powder, which is enriched in the 100Mo
isotope, is of particular interest as it is the source of 100Mo in the
crystals. A high-purity germanium detector having 100% relative efficiency,
named CC1, is being operated in the Yangyang underground laboratory. Using CC1,
we collected a gamma spectrum from a 1.6-kg 100EnrMoO3 powder sample enriched
to 96.4% in 100Mo. Activities were analyzed for the isotopes 228Ac, 228Th,
226Ra, and 40K. They are long-lived naturally occurring isotopes that can
produce background signals in the region of interest for AMoRE. Activities of
both 228Ac and 228Th were < 1.0 mBq/kg at 90% confidence level (C.L.). The
activity of 226Ra was measured to be 5.1 \pm 0.4 (stat) \pm 2.2 (syst) mBq/kg.
The 40K activity was found as < 16.4 mBq/kg at 90% C.L.Comment: 20 pages, 6 figures, 5 table
Improved Abdominal Multi-Organ Segmentation via 3D Boundary-Constrained Deep Neural Networks
Quantitative assessment of the abdominal region from clinically acquired CT
scans requires the simultaneous segmentation of abdominal organs. Thanks to the
availability of high-performance computational resources, deep learning-based
methods have resulted in state-of-the-art performance for the segmentation of
3D abdominal CT scans. However, the complex characterization of organs with
fuzzy boundaries prevents the deep learning methods from accurately segmenting
these anatomical organs. Specifically, the voxels on the boundary of organs are
more vulnerable to misprediction due to the highly-varying intensity of
inter-organ boundaries. This paper investigates the possibility of improving
the abdominal image segmentation performance of the existing 3D encoder-decoder
networks by leveraging organ-boundary prediction as a complementary task. To
address the problem of abdominal multi-organ segmentation, we train the 3D
encoder-decoder network to simultaneously segment the abdominal organs and
their corresponding boundaries in CT scans via multi-task learning. The network
is trained end-to-end using a loss function that combines two task-specific
losses, i.e., complete organ segmentation loss and boundary prediction loss. We
explore two different network topologies based on the extent of weights shared
between the two tasks within a unified multi-task framework. To evaluate the
utilization of complementary boundary prediction task in improving the
abdominal multi-organ segmentation, we use three state-of-the-art
encoder-decoder networks: 3D UNet, 3D UNet++, and 3D Attention-UNet. The
effectiveness of utilizing the organs' boundary information for abdominal
multi-organ segmentation is evaluated on two publically available abdominal CT
datasets. A maximum relative improvement of 3.5% and 3.6% is observed in Mean
Dice Score for Pancreas-CT and BTCV datasets, respectively.Comment: 15 pages, 16 figures, journal pape
Approaches to developing tolerance and error budget for active three mirror anastigmat space telescopes
The size of the optics used in observatories is often limited by fabrication,
metrology, and handling technology, but having a large primary mirror provides
significant benefits for scientific research. The evolution of rocket launch
options enables heavy payload carrying on orbit and outstretching the
telescope's form-factor choices. Moreover, cost per launch is lower than the
traditional flight method, which is obviously advantageous for various novel
space observatory concepts. The University of Arizona has successfully
fabricated many large-scale primary optics for ground-based observatories
including the Large Binocular Telescope (LBT, 8.4 meter diameter two primary
mirrors), Large Synoptic Survey Telescope (now renamed to Vera C. Rubin
Observatory, 8.4 meter diameter monolithic primary and tertiary mirror), and
the Giant Magellan Telescope (GMT, 8.4 meter diameter primary mirror seven
segments). Launching a monolithic primary mirror into space could bypass many
of the difficulties encountered during the assembly and deployment of the
segmented primary mirrors. However, it might bring up unprecedented challenges
and hurdles, also. We explore and foresee the expected challenges and evaluate
them. To estimate the tolerance and optical error budget of a large optical
system in space such as three mirror anastigmat telescope, we have developed a
methodology that considers various errors from design, fabrication, assembly,
and environmental factors.Comment: 6 pages, presented August 2023 at SPIE Optics+Photonics, San Diego,
CA, US
Mutagenesis of Trichoderma reesei endoglucanase I: impact of expression host on activity and stability at elevated temperatures.
BackgroundTrichoderma reesei is a key cellulase source for economically saccharifying cellulosic biomass for the production of biofuels. Lignocellulose hydrolysis at temperatures above the optimum temperature of T. reesei cellulases (~50°C) could provide many significant advantages, including reduced viscosity at high-solids loadings, lower risk of microbial contamination during saccharification, greater compatibility with high-temperature biomass pretreatment, and faster rates of hydrolysis. These potential advantages motivate efforts to engineer T. reesei cellulases that can hydrolyze lignocellulose at temperatures ranging from 60-70°C.ResultsA B-factor guided approach for improving thermostability was used to engineer variants of endoglucanase I (Cel7B) from T. reesei (TrEGI) that are able to hydrolyze cellulosic substrates more rapidly than the recombinant wild-type TrEGI at temperatures ranging from 50-70°C. When expressed in T. reesei, TrEGI variant G230A/D113S/D115T (G230A/D113S/D115T Tr_TrEGI) had a higher apparent melting temperature (3°C increase in Tm) and improved half-life at 60°C (t1/2 = 161 hr) than the recombinant (T. reesei host) wild-type TrEGI (t1/2 = 74 hr at 60°C, Tr_TrEGI). Furthermore, G230A/D113S/D115T Tr_TrEGI showed 2-fold improved activity compared to Tr_TrEGI at 65°C on solid cellulosic substrates, and was as efficient in hydrolyzing cellulose at 60°C as Tr_TrEGI was at 50°C. The activities and stabilities of the recombinant TrEGI enzymes followed similar trends but differed significantly in magnitude depending on the expression host (Escherichia coli cell-free, Saccharomyces cerevisiae, Neurospora crassa, or T. reesei). Compared to N.crassa-expressed TrEGI, S. cerevisiae-expressed TrEGI showed inferior activity and stability, which was attributed to the lack of cyclization of the N-terminal glutamine in Sc_TrEGI and not to differences in glycosylation. N-terminal pyroglutamate formation in TrEGI expressed in S. cerevisiae was found to be essential in elevating its activity and stability to levels similar to the T. reesei or N. crassa-expressed enzyme, highlighting the importance of this ubiquitous modification in GH7 enzymes.ConclusionStructure-guided evolution of T. reesei EGI was used to engineer enzymes with increased thermal stability and activity on solid cellulosic substrates. Production of TrEGI enzymes in four hosts highlighted the impact of the expression host and the role of N-terminal pyroglutamate formation on the activity and stability of TrEGI enzymes
Ionic liquid-based rechargeable lithium metal-polymer cells assembled with Polyaniline/Carbon nanotube composite cathode
The Cut & Enhance method : selecting clusters of galaxies from the SDSS commissioning data
We describe an automated method, the Cut & Enhance method (CE) for detecting
clusters of galaxies in multi-color optical imaging surveys. This method uses
simple color cuts, combined with a density enhancement algorithm, to up-weight
pairs of galaxies that are close in both angular separation and color. The
method is semi-parametric since it uses minimal assumptions about cluster
properties in order to minimize possible biases. No assumptions are made about
the shape of clusters, their radial profile or their luminosity function. The
method is successful in finding systems ranging from poor to rich clusters of
galaxies, of both regular and irregular shape. We determine the selection
function of the CE method via extensive Monte Carlo simulations which use both
the real, observed background of galaxies and a randomized background of
galaxies. We use position shuffled and color shuffled data to perform the false
positive test. We have also visually checked all the clusters detected by the
CE method. We apply the CE method to the 350 deg^2 of the SDSS (Sloan Digital
Sky Survey) commissioning data and construct a SDSS CE galaxy cluster catalog
with an estimated redshift and richness for each cluster. The CE method is
compared with other cluster selection methods used on SDSS data such as the
Matched Filter (Postman et al. 1996, Kim et al. 2001), maxBCG technique (Annis
et al. 2001) and Voronoi Tessellation (Kim et al. 2001). The CE method can be
adopted for cluster selection in any multi-color imaging surveys.Comment: 62 pages, 32 figures, Accepted for publication in the Astronomical
Journal, "the CE galaxy cluster catalog can be downloaded from,
http://astrophysics.phys.cmu.edu/~tomo/ce/
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