2,156 research outputs found
Rotational modulation of the photospheric and chromospheric activity in the young, single K2-dwarf PW And
High resolution echelle spectra of PW And (HD~1405) have been taken during
eight observing runs from 1999 to 2002. The detailed analysis of the spectra
allow us to determine its spectral type (K2V), mean heliocentric radial
velocity (V_hel = -11.15 km/s) rotational velocity (vsin{i} = 22.6 km/s), and
equivalent width of the lithium line 6707.8 AA (EW(LiI) = 273 mAA). The
kinematic (Galactic Velocity (U, V, W)) confirms its membership of the Local
Association moving group, in agreement with the age (30 to 80 Myrs) inferred
from the color magnitude diagram and the lithium equivalent width. Photospheric
activity (presence of cool spots that disturb the profiles of the photospheric
lines) has been detected as changes in the the bisectors of the cross
correlation function (CCF) resulting of cross-correlate the spectra of PW And
with the spectrum of a non active star of similar spectral type. These
variations of the CCF bisectors are related to the variations in the measured
radial velocities and are modulated with a period similar to the photometric
period of the star. At the same time, chromospheric activity has been analyzed,
using the spectral subtraction technique and simultaneous spectroscopic
observations of the H_alpha, H_beta, NaI D_1 and D_2$, HeI D_3, MgI b triplet,
CaII H&K, and CaII infrared triplet lines. A flare was observed during the last
observing run of 2001, showing an enhancement in the observed chromospheric
lines. A less powerful flare was observed on 2002 August 23. The variations of
the chromospheric activity indicators seem to be related to the photospheric
activity. A correlation between radial velocity, changes in the CCF bisectors
and equivalent width of different chromospheric lines is observed with a
different behaviour between epochs 1999, 2001 and 2002.Comment: Latex file with 20 pages, 21 figures tar'ed gzip'ed. Full postscript
(text, figures and tables) available at
http://www.ucm.es/info/Astrof/users/dmg/pub_dmg.html Accepted for publication
in: Astronomy & Astrophysics (A&A
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On-Board Sensor-Based NO x Emissions from Heavy-Duty Diesel Vehicles
Real-world
nitrogen oxides (NOx) emissions
were estimated using on-board sensor readings from 72 heavy-duty diesel
vehicles (HDDVs) equipped with a Selective Catalytic Reduction (SCR)
system in California. The results showed that there were large differences
between in-use and certification NOx emissions,
with 12 HDDVs emitting more than three times the standard during hot-running
and idling operations in the real world. The overall NOx conversion efficiencies of the SCR system on many
vehicles were well below the 90% threshold that is expected for an
efficient SCR system, even when the SCR system was above the optimum
operating temperature threshold of 250 °C. This could potentially
be associated with SCR catalyst deterioration on some engines. The
Not-to-Exceed (NTE) requirements currently used by the heavy-duty
in-use compliance program were evaluated using on-board NOx sensor data. Valid NTE events covered only 4.2–16.4%
of the engine operation and 6.6–34.6% of the estimated NOx emissions. This work shows that low cost
on-board NOx sensors are a convenient
tool to monitor in-use NOx emissions in
real-time, evaluate the SCR system performance, and identify vehicle
operating modes with high NOx emissions.
This information can inform certification and compliance programs
to ensure low in-use NOx emissions
Hard Metal Production by ERS: Processing Parameter Roles in Final Properties
Cemented carbide is a hard composite material, used widely in a variety of industries. The value of the global tungsten carbide market is expected to grow by 4.4% (compound annual growth rate) from 2017 to 2022. One of the main markets is in metal cutting and wear parts, where small pieces (or inserts), a few grams in weight, are used. Field-assisted sintering technique (FAST) technologies allow for the production of small blanks in a single step from powder, which are near final dimensions. Production cycles are very short. In this paper, one of the FAST processes, the ERS technology, is applied to obtain WC10Co parts. A review of the process variable effects on the final properties of the parts is accomplished. Final properties of a range of conventionally produced inserts are obtained, using 100 MPa compacting pressure, 80 MA/m2 of current density, and processing times of around 800 ms.This research was funded by EU, grant number FoF.NMP.2013-10 608729 (7th Framework
Programme) EFFIPRO
Extreme late-summer drought causes neutral annual carbon balance in southwestern ponderosa pine forests and grasslands
We assessed the impacts of extreme late-summer drought on carbon balance in a semi-arid forest region in Arizona. To understand drought impacts over extremes of forest cover, we measured net ecosystem production (NEP), gross primary production (GPP), and total ecosystem respiration (TER) with eddy covariance over five years (2006-10) at an undisturbed ponderosa pine (Pinus ponderosa) forest and at a former forest converted to grassland by intense burning. Drought shifted annual NEP from a weak source of carbon to the atmosphere to a neutral carbon balance at the burned site and from a carbon sink to neutral at the undisturbed site. Carbon fluxes were particularly sensitive to drought in August. Drought shifted August NEP at the undisturbed site from sink to source because the reduction of GPP (70%) exceeded the reduction of TER (35%). At the burned site drought shifted August NEP from weak source to neutral because the reduction of TER (40%) exceeded the reduction of GPP (20%). These results show that the lack of forest recovery after burning and the exposure of undisturbed forests to late-summer drought reduce carbon sink strength and illustrate the high vulnerability of forest carbon sink strength in the southwest US to predicted increases in intense burning and precipitation variability
Exercise Prior to Pregnancy Enhances the Suppressive Function of Tregs in Offspring in a Mouse Model of Asthma
Regulatory T cells (Tregs) are a specialized subset of T cells responsible for peripheral tolerance and the mediation of inappropriate immune responses, such as those seen in asthma and allergy. Our lab is interested in the role that exercise plays in Treg responses. Using a mouse model of asthma, we have shown that exercise increases both the number and suppressive function of Tregs. It has been shown that exposing nursing dams to allergens confers protection against airway hyperresponsiveness and inflammation (trademarks of asthma) in pups exposed to the same allergen. In the present study, we wanted to determine if the exercise-induced increase in number and suppressive function of Tregs would be similarly passed from dams to their pups. Male pups from dams that were exercised prior to pregnancy (E) and pups from sedentary dams (S) were OVA-sensitized and challenged beginning at 4wks of age. Mice were sacrificed and tissues were taken for cell analysis. When co-cultured with CD4+CD25- responder cells, Tregs from E pups enhanced suppression of responder cells between 8.4-10% when compared to Tregs from S pups. While the number of Tregs from the mediastinal lymph node was not significantly different between E and S pups, there was a significant decrease in the number of CD4+ and CD8+ T cells in E pups from S pups (51.24% + 10.2 vs. 33.51% + 3.3 and 21.42% + 7.3 vs. 12.94% + 1.2, respectively), indicating a reduction in cellular infiltration and a muted immune response to allergen. Although not significant, there was a doubling of the number of Tregs in the thymus and bone marrow of E pups compared to S pups. This study indicates that exercise prior to pregnancy may confer some Treg-mediated protection against asthma
Measuring the flatness of focal plane for very large mosaic CCD camera
Large mosaic multiCCD camera is the key instrument for modern digital sky
survey. DECam is an extremely red sensitive 520 Megapixel camera designed for
the incoming Dark Energy Survey (DES). It is consist of sixty two 4k2k
and twelve 2k x 2k 250-micron thick fully-depleted CCDs, with a focal plane of
44 cm in diameter and a field of view of 2.2 square degree. It will be attached
to the Blanco 4-meter telescope at CTIO. The DES will cover 5000 square-degrees
of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years
starting from 2011.
To achieve the science goal of constraining the Dark Energy evolution,
stringent requirements are laid down for the design of DECam. Among them, the
flatness of the focal plane needs to be controlled within a 60-micron envelope
in order to achieve the specified PSF variation limit. It is very challenging
to measure the flatness of the focal plane to such precision when it is placed
in a high vacuum dewar at 173 K. We developed two image based techniques to
measure the flatness of the focal plane. By imaging a regular grid of dots on
the focal plane, the CCD offset along the optical axis is converted to the
variation the grid spacings at different positions on the focal plane. After
extracting the patterns and comparing the change in spacings, we can measure
the flatness to high precision. In method 1, the regular dots are kept in high
sub micron precision and cover the whole focal plane. In method 2, no high
precision for the grid is required. Instead, we use a precise XY stage moves
the pattern across the whole focal plane and comparing the variations of the
spacing when it is imaged by different CCDs. Simulation and real measurements
show that the two methods work very well for our purpose, and are in good
agreement with the direct optical measurements.Comment: Presented at SPIE Conference,Ground-based and Airborne
Instrumentation for Astronomy III, San Diego, 201
Diagnostic accuracy of health care administrative diagnosis codes to identify nontuberculous mycobacteria disease: A systematic review
Background: Health care administrative database research frequently uses standard medical codes to identify diagnoses or procedures. The aim of this review was to establish the diagnostic accuracy of codes used in administrative data research to identify nontuberculous mycobacterial (NTM) disease, including lung disease (NTMLD).
Methods: We searched Ovid Medline, Embase, Scopus, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from inception to April 2019. We included studies assessing the diagnostic accuracy of
Results: We identified 5549 unique citations. Of the 96 full-text articles reviewed, 7 eligible studies of moderate quality (3730 participants) were included in our review. The diagnostic accuracy of ICD-9-CM diagnosis codes to identify NTM disease varied widely across studies, with positive predictive values ranging from 38.2% to 100% and sensitivity ranging from 21% to 93%. For NTMLD, 4 studies reported diagnostic accuracy, with positive predictive values ranging from 57% to 64.6% and sensitivity ranging from 21% to 26.9%.
Conclusions: Diagnostic accuracy measures of codes used in health care administrative data to identify patients with NTM varied across studies. Overall the positive predictive value of ICD-9-CM diagnosis codes alone is good, but the sensitivity is low; this method is likely to underestimate case numbers, reflecting the current limitations of coding systems to capture NTM diagnoses
Circumventing UV light induced nano-morphology disorder to achieve long lifetime PTB7-Th:PCBM based solar cells
Large area flexible electronics rely on organic or hybrid materials prone to degradation limiting the device lifetime. For many years, photo-oxidation has been thought to be one of the major degradation pathways. However, intense illumination may lead to a burn-in or a rapid decrease in performance for devices completely isolated from corrosive elements as oxygen or moisture. The experimental studies we present in here indicate that a plausible triggering for the burn-in is a spin flip after a UV photon absorption leading to the accumulation of electrostatic potential energy that initiates a rapid destruction of the nano-morpholgy in the fullerene phase of a polymer cell. To circumvent this and achieve highly stable and efficient devices, we induce a robust nano-crystalline ordering in the PCBM phase prior to UV illumination. In that event, PTB7-Th:PC71BM cells are shown to exhibit T80 lifetimes larger than 1.6 years under a continuous UV-filtered 1-sun illumination, equivalent to 7 years for sunlight harvesting at optimal orientation and 10 years for vertical applications.Peer ReviewedPostprint (author's final draft
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