1,387 research outputs found
JPL preferred parts list: Reliable electronic components
The JPL Preferred Parts List was prepared to provide a basis for selection of electronic parts for JPL spacecraft programs. Supporting tests for the listed parts were designed to comply with specific spacecraft environmental requirements. The list tabulates the electronic, magnetic, and electromechanical parts applicable to all JPL electronic equipment wherein reliability is a major concern. The parts listed are revelant to equipment supplied by subcontractors as well as fabricated at the laboratory
Perceptions of volcanic air pollution and exposure reduction practices on the Island of Hawai‘i: Working towards socially relevant risk communication
Kīlauea volcano, on the Island of Hawai‘i, is one of the most active volcanoes in the world. Over the past four decades it has released large amounts of volcanic gases and aerosols which form volcanic air pollution known as ‘vog’. Communities downwind of Kīlauea have been chronically or episodically exposed to this potentially harmful air pollution and have raised concerns about the hazards of vog exposure. Public health and civil protection agencies have offered a range of advice, information, and mitigation strategies for living with vog. In this mixed-methods social study, we investigate the translation of official advice into practice in Island of Hawai‘i communities and assess how risk communication could be improved by considering public input, preferences, and community relevance. Given the paucity of information on the long-term effects of chronic vog exposure, assessing the effectiveness of public health and risk communication is vital.In 2015, through questionnaire surveys (n = 143), four focus groups and several stakeholder meetings, we assessed whether, and how, residents accessed intervention advice, if it was relevant and useful, how they acted on it and how they would like to receive advice and urgent exposure warnings in the future. We also investigated local knowledge and self-developed interventions and documented the perceived risks of vog exposure, including symptoms that people attribute to vog.Most participants (83%) perceived that vog caused health symptoms such as exacerbation of asthma, itchy eyes, and blocked nose and 62% thought it was harmful to their long-term health. A third of participants had considered relocating to avoid the vog yet, despite this, most people took no action to reduce vog exposure. Participants reported that the official advice was difficult to follow given their living situation or lifestyle. Some participants viewed the agency advice as inconsistent, irrelevant, or out of date. Participants preferred to receive advice and air quality alerts via a variety of media, depending on factors such as their access to internet, cell phone, and radio reception.The study findings led to a collaboration with federal and state health, land management, educational, science, and civil protection agencies to improve and standardize health advisory messaging, to make it more relevant to Island of Hawai‘i communities and environment. New printable and web-based communication products were developed, which included local knowledge of effective protective actions/symptom reduction strategies. An interagency ‘Vog Dashboard’ was also introduced to consolidate vog knowledge, including sources of air quality data, vog forecasts, and advice on vog environmental, agricultural, and health impacts. This dashboard was recommended as a primary site for advice by international media outlets in 2018 and was heavily used during the 2018 Kīlauea and 2022 Mauna Loa eruption crises
The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
Open clusters are collections of stars with a single, well-determined age,
and can be used to investigate the connections between angular-momentum
evolution and magnetic activity over a star's lifetime. We present the results
of a comparative study of the relationship between stellar rotation and
activity in two benchmark open clusters: Praesepe and the Hyades. As they have
the same age and roughly solar metallicity, these clusters serve as an ideal
laboratory for testing the agreement between theoretical and empirical
rotation-activity relations at 600 Myr. We have compiled a sample of
720 spectra --- more than half of which are new observations --- for 516
high-confidence members of Praesepe; we have also obtained 139 new spectra for
130 high-confidence Hyads. We have collected rotation periods () for
135 Praesepe members and 87 Hyads. To compare emission, an indicator
of chromospheric activity, as a function of color, mass, and Rossby number
, we first calculate an expanded set of values, with which we can
obtain the to bolometric luminosity ratio, ,
even when spectra are not flux-calibrated and/or stars lack reliable distances.
Our values cover a broader range of stellar masses and colors (roughly
equivalent to spectral types from K0 to M9), and exhibit better agreement
between independent calculations, than existing values. We find no difference
between the two clusters in their equivalent width or
distributions, and therefore take the merged
and data to be representative of 600-Myr-old stars. Our analysis
shows that activity in these stars is saturated for
. Above that value activity declines as a
power-law with slope , before dropping off rapidly
at ...Comment: 17 pages, 15 figures, Accepted by Ap
The WCRP CMIP3 multi-model dataset: a new era in climate change research
A coordinated set of global coupled climate model [atmosphere–ocean general circulation model (AOGCM)] experiments for twentieth- and twenty-first-century climate, as well as several climate change commitment and other experiments, was run by 16 modeling groups from 11 countries with 23 models for assessment in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Since the assessment was completed, output from another model has been added to the dataset, so the participation is now 17 groups from 12 countries with 24 models. This effort, as well as the subsequent analysis phase, was organized by the World Climate Research Programme (WCRP) Climate Variability and Predictability (CLIVAR) Working Group on Coupled Models (WGCM) Climate Simulation Panel, and constitutes the third phase of the Coupled Model Intercomparison Project (CMIP3). The dataset is called the WCRP CMIP3 multimodel dataset, and represents the largest and most comprehensive international global coupled climate model experiment and multimodel analysis effort ever attempted. As of March 2007, the Program for Climate Model Diagnostics and Intercomparison (PCMDI) has collected, archived, and served roughly 32 TB of model data. With oversight from the panel, the multimodel data were made openly available from PCMDI for analysis and academic applications. Over 171 TB of data had been downloaded among the more than 1000 registered users to date. Over 200 journal articles, based in part on the dataset, have been published so far. Though initially aimed at the IPCC AR4, this unique and valuable resource will continue to be maintained for at least the next several years. Never before has such an extensive set of climate model simulations been made available to the international climate science community for study. The ready access to the multimodel dataset opens up these types of model analyses to researchers, including students, who previously could not obtain state-of-the-art climate model output, and thus represents a new era in climate change research. As a direct consequence, these ongoing studies are increasing the body of knowledge regarding our understanding of how the climate system currently works, and how it may change in the future
The Angular Momentum Content and Evolution of Class I and Flat-Spectrum Protostars
We report on the angular momentum content of heavily embedded protostars
based on our analysis of the projected rotation velocities (v sin i s) of 38
Class I/flat spectrum young stellar objects presented by Doppmann et al (2005).
After correcting for projection effects, we find that infrared-selected Class
I/flat spectrum objects rotate significantly more quickly (median equatorial
rotation velocity ~ 38 km/sec) than Classical T Tauri stars (CTTSs; median
equatorial rotation velocity ~ 18 km/sec) in the Rho Ophiuchi and
Taurus-Aurigae regions. The detected difference in rotation speeds between
Class I/flat spectrum sources and CTTSs proves difficult to explain without
some mechanism which transfers angular momentum out of the protostar between
the two phases. Assuming Class I/flat spectrum sources possess physical
characteristics (M_*,R_*,B_*) typical of pre-main sequence stars, fully disk
locked Class I objects should have co-rotation radii within their protostellar
disks that match well (within 30%) with the predicted magnetic coupling radii
of Shu et al (1994). The factor of two difference in rotation rates between
Class I/flat spectrum and CTTS sources, when interpreted in the context of disk
locking models, also imply a factor of 5 or greater difference in mass
accretion rates between the two phases.Comment: 13 pages, 6 figures. Accepted for publication in the Astronomical
Journal (tentatively for June 2005 edition
The Factory and the Beehive III: PTFEB132.707+19.810, a Low-Mass Eclipsing Binary in Praesepe Observed by PTF and K2
Theoretical models of stars constitute a fundamental bedrock upon which much
of astrophysics is built, but large swaths of model parameter space remain
uncalibrated by observations. The best calibrators are eclipsing binaries in
clusters, allowing measurement of masses, radii, luminosities, and
temperatures, for stars of known metallicity and age. We present the discovery
and detailed characterization of PTFEB132.707+19.810, a P=6.0 day eclipsing
binary in the Praesepe cluster (~600--800 Myr; [Fe/H]=0.140.04). The
system contains two late-type stars (SpT=M3.50.2;
SpT=M4.30.7) with precise masses (~;
~) and radii (~;
~). Neither star meets the predictions of stellar
evolutionary models. The primary has the expected radius, but is cooler and
less luminous, while the secondary has the expected luminosity, but is cooler
and substantially larger (by 20%). The system is not tidally locked or
circularized. Exploiting a fortuitous 4:5 commensurability between
and , we demonstrate that fitting errors from the unknown spot
configuration only change the inferred radii by <1--2%. We also analyze subsets
of data to test the robustness of radius measurements; the radius sum is more
robust to systematic errors and preferable for model comparisons. We also test
plausible changes in limb darkening, and find corresponding uncertainties of
~1%. Finally, we validate our pipeline using extant data for GU Boo, finding
that our independent results match previous radii to within the mutual
uncertainties (2--3%). We therefore suggest that the substantial discrepancies
are astrophysical; since they are larger than for old field stars, they may be
tied to the intermediate age of PTFEB132.707+19.810.Comment: Accepted to ApJ; 36 pages, 19 figures, 8 tables in two-column AASTEX6
forma
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