310 research outputs found
Technical and economic feasibility of centralized facilities for solar hydrogen production via photocatalysis and photoelectrochemistry
Photoelectrochemical water splitting is a promising route for the renewable production of hydrogen fuel. This work presents the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology. The four reactor types considered were a single bed particle suspension system, a dual bed particle suspension system, a fixed panel array, and a tracking concentrator array. The current performance of semiconductor absorbers and electrocatalysts were considered to compute reasonable solar-to-hydrogen conversion efficiencies for each of the four systems. The U.S. Department of Energy H2A model was employed to calculate the levelized cost of hydrogen output at the plant gate at 300 psi for a 10 tonne per day production scale. All capital expenditures and operating costs for the reactors and auxiliaries (compressors, control systems, etc.) were considered. The final cost varied from 10.40 per kg H2 with the particle bed systems having lower costs than the panel-based systems. However, safety concerns due to the cogeneration of O_2 and H_2 in a single bed system and long molecular transport lengths in the dual bed system lead to greater uncertainty in their operation. A sensitivity analysis revealed that improvement in the solar-to-hydrogen efficiency of the panel-based systems could substantially drive down their costs. A key finding is that the production costs are consistent with the Department of Energy's targeted threshold cost of 4.00 per kg H_2 for dispensed hydrogen, demonstrating that photoelectrochemical water splitting could be a viable route for hydrogen production in the future if material performance targets can be met
An infrared survey of brightest cluster galaxies: Paper I
We report on an imaging survey with the Spitzer Space Telescope of 62
brightest cluster galaxies with optical line emission. These galaxies are
located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky
Survey. We find that about half of these sources have a sign of excess infrared
emission; 22 objects out of 62 are detected at 70 microns, 18 have 8 to 5.8
micron flux ratios above 1.0 and 28 have 24 to 8 micron flux ratios above 1.0.
Altogether 35 of 62 objects in our survey exhibit at least one of these signs
of infrared excess. Four galaxies with infrared excesses have a 4.5/3.6 micron
flux ratio indicating the presence of hot dust, and/or an unresolved nucleus at
8 microns. Three of these have high measured [OIII](5007A)/Hbeta flux ratios
suggesting that these four, Abell 1068, Abell 2146, and Zwicky 2089, and
R0821+07, host dusty active galactic nuclei (AGNs). 9 objects (including the
four hosting dusty AGNs) have infrared luminosities greater than 10^11 L_sol
and so can be classified as luminous infrared galaxies (LIRGs). Excluding the
four systems hosting dusty AGNs, the excess mid-infrared emission in the
remaining brightest cluster galaxies is likely related to star formation.Comment: accepted for publication in ApJ
HST NIR Snapshot Survey of 3CR Radio Source Counterparts II: An Atlas and Inventory of the Host Galaxies, Mergers and Companions
We present the second part of an H-band (1.6 microns) atlas of z<0.3 3CR
radio galaxies, using the Hubble Space Telescope Near Infrared Camera and
Multi-Object Spectrometer (HST NICMOS2). We present new imaging for 21 recently
acquired sources, and host galaxy modeling for the full sample of 101
(including 11 archival) -- an 87% completion rate. Two different modeling
techniques are applied, following those adopted by the galaxy morphology and
the quasar host galaxy communities. Results are compared, and found to be in
excellent agreement, although the former breaks down in the case of strongly
nucleated sources. Companion sources are tabulated, and the presence of
mergers, tidal features, dust disks and jets are catalogued. The tables form a
catalogue for those interested in the structural and morphological dust-free
host galaxy properties of the 3CR sample, and for comparison with morphological
studies of quiescent galaxies and quasar host galaxies. Host galaxy masses are
estimated, and found to typically lie at around 2*10^11 solar masses. In
general, the population is found to be consistent with the local population of
quiescent elliptical galaxies, but with a longer tail to low Sersic index,
mainly consisting of low-redshift (z<0.1) and low-radio-power (FR I) sources. A
few unusually disky FR II host galaxies are picked out for further discussion.
Nearby external sources are identified in the majority of our images, many of
which we argue are likely to be companion galaxies or merger remnants. The
reduced NICMOS data are now publicly available from our website
(http://archive.stsci.edu/prepds/3cr/)Comment: ApJS, 177, 148: Final version; includes revised figures 1, 15b, and
section 7.5 (and other minor changes from editing process. 65 pages, inc. 17
figure
AGN Selection and Demographics: A New Age with JWST/MIRI
Understanding the co-evolution of supermassive black holes (SMBHs) and their
host systems requires a comprehensive census of active galactic nuclei (AGN)
behavior across a wide range of redshift, luminosity, obscuration level and
galaxy properties. We report significant progress with JWST towards this goal
from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey
(SMILES). Based on comprehensive SED analysis of 3273 MIRI-detected sources, we
identify 217 AGN candidates over a survey area of 34 arcmin,
including a primary sample of 111 AGNs in normal massive galaxies
() at 0--4, an extended sample of 86 AGN {\it
candidates} in low-mass galaxies () and a high-
sample of 20 AGN {\it candidates} at 4--8.4. Notably, about 80\% of our
MIRI-selected AGN candidates are new discoveries despite the extensive pre-JWST
AGN searches. Even among the massive galaxies where the previous AGN search is
believed to be thorough, 34\% of the MIRI AGN identifications are new,
highlighting the impact of obscuration on previous selections. By combining our
results with the efforts at other wavelengths, we build the most complete AGN
sample to date and examine the relative performance of different selection
techniques. We find the obscured AGN fraction increases from to and then drops towards higher
luminosity. Additionally, the obscured AGN fraction gradually increases from
to with most high- AGNs obscured. We discuss how AGN
obscuration, intrinsic SED variations, galaxy contamination, survey depth and
selection techniques complicate the construction of a complete AGN sample.Comment: 32 pages, 21 figures, submitted to Ap
Participatory monitoring and evaluation approaches that influence decision-making: lessons from a maternal and newborn study in Eastern Uganda
BACKGROUND: The use of participatory monitoring and evaluation (M&E) approaches is important for guiding local
decision-making, promoting the implementation of effective interventions and addressing emerging issues in the
course of implementation. In this article, we explore how participatory M&E approaches helped to identify key design
and implementation issues and how they influenced stakeholdersâ decision-making in eastern Uganda.
METHOD: The data for this paper is drawn from a retrospective reflection of various M&E approaches used in a maternal
and newborn health project that was implemented in three districts in eastern Uganda. The methods included qualitative
and quantitative M&E techniques such as key informant interviews, formal surveys and supportive
supervision, as well as participatory approaches, notably participatory impact pathway analysis.
RESULTS: At the design stage, the M&E approaches were useful for identifying key local problems and feasible
local solutions and informing the activities that were subsequently implemented. During the implementation
phase, the M&E approaches provided evidence that informed decision-making and helped identify emerging
issues, such as weak implementation by some village health teams, health facility constraints such as poor use of standard
guidelines, lack of placenta disposal pits, inadequate fuel for the ambulance at some facilities, and poor care for low birth
weight infants. Sharing this information with key stakeholders prompted them to take appropriate actions. For example,
the sub-county leadership constructed placenta disposal pits, the district health officer provided fuel for ambulances, and
health workers received refresher training and mentorship on how to care for newborns.
CONCLUSION: Diverse sources of information and perspectives can help researchers and decision-makers understand and
adapt evidence to contexts for more effective interventions. Supporting districts to have crosscutting, routine information
generating and sharing platforms that bring together stakeholders from different sectors is therefore crucial for the successful
implementation of complex development interventions
External influences and priority-setting for anti-cancer agents: a case study of media coverage in adjuvant trastuzumab for breast cancer
<p>Abstract</p> <p>Background</p> <p>Setting priorities for the funding of new anti-cancer agents is becoming increasingly complex. The funding of adjuvant trastuzumab for breast cancer has brought this dilemma to the fore. In this paper we review external factors that may influence decision-making bodies and present a case study of media response in Ontario, Canada to adjuvant trastuzumab for breast cancer.</p> <p>Methods</p> <p>A comprehensive search of the databases of Canadian national and local newspapers and television was performed. Articles pertaining to trastuzumab in adjuvant breast cancer as well as 17 other anti-cancer drugs and indications were retrieved. The search period was from the date when individual trial results were announced to the date funding was made available in Ontario.</p> <p>Results</p> <p>During the 2.6 months between the release of the trastuzumab results to funding approval in Ontario, we identified 51 episodes of media coverage. For the 17 other drugs/indications (7 breast and 10 non-breast), the median time to funding approval was 31 months (range 14â46). Other recent major advances in oncology such as adjuvant vinorelbine/cisplatin for resected NSCLC and docetaxel for advanced prostate cancer received considerably less media attention (17 media reports for each) than trastuzumab. The median number of media reports for breast cancer drugs was 4.5 compared to 2.5 for non-breast cancer drugs (p = 0.56).</p> <p>Conclusion</p> <p>Priority-setting for novel anti-cancer agents is a complex process that tries to ensure fair use of constrained resources to fund therapies with the best evidence of clinical benefit. However, this process is subject to external factors including the influence of media, patient advocates, politicians, and industry. The data in this case study serve to illustrate the significant involvement one (or all) of these external factors may play in the debate over priority-setting.</p
Reproductive aspects of the oceanic whitetip shark, Carcharhinus longimanus (Elasmobranchii: Carcharhinidae), in the equatorial and southwestern Atlantic Ocean
The present study sought to study the reproductive biology of the oceanic whitetip shark, Carcharhinus longimanus, in the equatorial and southwestern Atlantic Ocean. A total of 234 specimens were collected as bycatch during pelagic longline fisheries targeting tunas and swordfish, between December 2003 and December 2010. The fishing area was located between latitudes 10N and 35S and longitudes 3E and 40W. Of the 234 individuals sampled, 118 were females (with sizes ranging from 81 to 227 cm TL, total length) and 116 males (ranging from 80 to 242 cm TL). The reproductive stages of the females were classed as immature, mature, preovulatory and pregnant, while males were divided into immature, maturing and mature. The size at maturity for females was estimated at 170.0 cm TL, while that for males was between 170.0 and 190.0 cm TL. Ovarian fecundity ranged from 1 to 10 follicles and uterine fecundity from 1 to 10 embryos. The reproductive cycle of this species is most likely biennial, with parturition occurring once every two years.info:eu-repo/semantics/publishedVersio
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