750 research outputs found
Unveiling Dust-enshrouded Star Formation in the Early Universe: a Sub-mm Survey of the Hubble Deep Field
The advent of sensitive sub-mm array cameras now allows a proper census of
dust-enshrouded massive star-formation in very distant galaxies, previously
hidden activity to which even the faintest optical images are insensitive. We
present the deepest sub-mm survey of the sky to date, taken with the SCUBA
camera on the James Clerk Maxwell Telescope and centred on the Hubble Deep
Field. The high source density found in this image implies that the survey is
confusion-limited below a flux density of 2 mJy. However, within the central 80
arcsec radius independent analyses yield 5 reproducible sources with S(850um) >
2 mJy which simulations indicate can be ascribed to individual galaxies. We
give positions and flux densities for these, and furthermore show using
multi-frequency photometric data that the brightest sources in our map lie at
redshifts z~3. These results lead to integral source counts which are
completely inconsistent with a no-evolution model, and imply that massive
star-formation activity continues at redshifts > 2. The combined brightness of
the 5 most secure sources in our map is sufficient to account for 30 - 50% of
the previously unresolved sub-mm background, and we estimate statistically that
the entire background is resolved at about the 0.3 mJy level. Finally we
discuss possible optical identifications and redshift estimates for the
brightest sources. One source appears to be associated with an extreme
starburst galaxy at z~1, whilst the remaining four appear to lie in the
redshift range 2 < z < 4. This implies a star-formation density over this
redshift range that is at least five times higher than that inferred from the
ultraviolet output of HDF galaxies.Comment: 19 pages, 6 figures (to appear as a Nature Article
A Submillimetre Survey of the Hubble Deep Field: Unveiling Dust-Enshrouded Star Formation in the Early Universe
The advent of sensitive sub-mm array cameras now allows a proper census of
dust-enshrouded massive star-formation in very distant galaxies, previously
hidden activity to which even the deepest optical images are insensitive. We
present the deepest sub-mm survey, taken with the SCUBA camera on the James
Clerk Maxwell Telescope (JCMT) and centred on the Hubble Deep Field (HDF). The
high source density on this image implies that the survey is confusion-limited
below a flux density of 2 mJy. However within the central 80 arcsec radius
independent analyses yield 5 reproducible sources with S(850um) > 2 mJy which
simulations indicate can be ascribed to individual galaxies. These data lead to
integral source counts which are completely inconsistent with a no evolution
model, whilst the combined brightness of the 5 most secure sources in our map
is sufficient to account for 30-50% of the previously unresolved sub-mm
background, and statistically the entire background is resolved at about the
0.3 mJy level. Four of the five brightest sources appear to be associated with
galaxies which lie in the redshift range 2 < z < 4. With the caveat that this
is a small sample of sources detected in a small survey area, these submm data
imply a star-formation density over this redshift range that is at least five
times higher than that inferred from the rest-frame ultraviolet output of HDF
galaxies.Comment: to appear in the proceedings of `The Birth of Galaxies', Xth
Rencontres de Blois, 4 pages, 1 postscript figure, uses blois.sty (included
The Resource Demand of Terawatt-Scale Perovskite Tandem Photovoltaics
Photovoltaics (PV) is the most important energy conversion technology for
cost-efficient climate change mitigation. To reach the international climate
goals, the annual PV module production capacity must be expanded to
multi-terawatt scale. Economic and resource constraints demand the
implementation cost-efficient multi-junction technologies, for which
perovskite-based tandem technologies are highly promising. In this work, the
resource demand of the emerging perovskite PV technology is investigated,
considering two factors of supply criticality, namely mining capacity for
minerals, as well as production capacity for synthetic materials. Overall, the
expansion of perovskite PV to a multi-terawatt scale may not be limited by
material supply if certain materials, especially cesium and indium, can be
replaced. Moreover, organic charge transport materials face unresolved
scalability challenges. This study demonstrates that, besides the improvement
of efficiency and stability, perovskite PV research needs also to be guided by
sustainable materials choices and design-for-recycling considerations
Solar decathlon : Show-Me solar team
Project Leaders: Barbara Buffaloe, Katie-Grantham-Lough, Michael Goldschmidt, Robert Stone, Luke Sudkamp, Paul Bilger, Anna Fleischer, Chris Krueger, Heather Benson, Anne Felts, Adam Smith, Renee Henry, Ben Brannon, Ruth Brent Tofle, Jo Britt-Rankin, Marjorie Sable"University of Missouri--Columbia (MU) and the Missouri University of Science & Technology (S&T) have composed the "Show-Me Solar Team." This team is composed of undergraduate and graduate students with a goal to design and build the most attractive, effective, and energy-efficient solar-powered house for the 2009 Solar Decathlon. The Solar Decathlon, an international design competition, exists to educate the public on solar energy, energy efficiency, and the best in home design. While this effort is well over the budget available for the current funding opportunity, we have selected certain components for submission in this application. Specifically, this effort includes architecture, interior design, architectural engineering, electrical engineering, civil engineering, history, and business disciplines across two campuses in a unique experience for all involved and utilizes technology and IT communications to make it happen. Most of the components of the project are done through computer and the virtual world. The students must rely on the ability to communicate via the internet for most decisions because only occasional face-to-face meetings take place. In addition, students on both campuses utilize computer programs related to their discipline and learn programs associated with other disciplines due to the multidisciplinary efforts required. For example, MU students often use Google Sketch?up to convey the architectural elements of the home. S&T students, new to Google Sketch-up, have found that with a tutorial by MU that they can better understand the dialogue going on between the teams on the design. We believe that the Show-Me Solar teamïżœs proposal for the Interdisciplinary Innovation Fund meets the requirements from the MU Information Technology Committee. The student-led team is working hard to make the University of Missouri system a leader in the next wave of home design through the use of innovative technology and strong relationships between disciplines. We look forward to working with the MUITC and hope that our combined effort will continue to foster interdisciplinary projects throughout the UM system. Please let us know if any further clarification is needed." --DescriptionMU Interdisciplinary Innovations Fun
Report on Archaeological Investigations Conducted at the St. Mary's Site (18AP45), 107 Duke of Gloucester Street, Annapolis, Maryland, 1987-1990
In celebration of the 250th anniversary of the birth of Charles Carroll of Carrollton, Archaeology in Annapolis was invited to excavate the Carroll House and garden on 107 Duke of Gloucester Street in Annapolis, Maryland. The site, named the St. Mary's Site (18AP45) for the Catholic church on the property, is currently owned by the Redemptorists, a Roman Catholic congregation of priests and brothers who have occupied the site since 1852. Prior to the Redemptorists' tenure, the site was owned by the Carroll family from 1701-1852 and is perhaps best known as the home of Charles Carroll of Carrollton (1737-1832), signer of the Declaration of Independence. Excavations at the site were conducted during four consecutive summer seasons from 1987-1990. The investigation focused on three research questions. The first line of inquiry were questions surrounding the dating, architectural configuration, and artifact deposits of the "frame house," a structure adjoining the west wall of the brick Carroll House via a "passage" and later a three story addition. The frame house was partially demolished in the mid-nineteenth century but the construction was thought to pre-date the brick portion of the house. The second research question was spurred by documentary research which indicated that the property might have been the location of Proctor's Tavern, a late 17th-century tavern which served as the meeting place of the Maryland Provincial Assembly. Archaeological testing hoped to determine its location and, if found, investigate Annapolis' early Euro-American occupation. The third research question focused on the landscape of the site as it was shaped by its occupants over the past three hundred years. The research questions included investigating the stratigraphy, geometry, and architectural and planting features of Charles Carroll of Carrollton's terraced garden built during the 1770s, and investigating the changes to the landscape made by the Redemptorists in the nineteenth and twentieth centuries. While no structural evidence associated with Proctorâs Tavern was uncovered during limited
excavations along Spa Creek, the historic shore of Spa Creek was identified, buried beneath deep
fill deposits laid down during construction of the Carroll Garden. Features and deposits associated
with this period likely remain intact in a waterlogged environment along the southeastern sea wall at
the St. Maryâs Site. Evidence of extensive earth moving by Carroll is present in the garden and was
identified during excavation and coring. This strongly suggests that the garden landscape visible at
the St. Maryâs Site is the intact Carroll Garden, which survives beneath contemporary and late nineteenth
century strata. The extant surviving garden should be considered highly sensitive to
ground-disturbing activities, and is also highly significant considering demonstrable associations
with the Carroll family. Other garden-related features were also discovered, including planting
holes, and a brick pavilion or parapet located along Spa Creek to the south of the site. The Duke of
Gloucester Street wall was shown to be associated with the Carroll occupation of the site. Finally,
intensive archaeological research was directed at the vicinity of a frame house constructed and
occupied by the Carrolls to the east of the existing brick house, which was replaced by the
Redemptorists in the nineteenth century with a greenhouse. These superimposed buildings were
documented in detail and remain highly significant features at the St. Maryâs Site
Multiple Sclerosis Followed by Neuromyelitis Optica Spectrum Disorder: From the National Multiple Sclerosis Society Case Conference Proceedings
A woman presented at age 18 years with partial myelitis and diplopia and experienced multiple subsequent relapses. Her MRI demonstrated T2 abnormalities characteristic of multiple sclerosis (MS) (white matter ovoid lesions and Dawson fingers), and CSF demonstrated an elevated IgG index and oligoclonal bands restricted to the CSF. Diagnosed with clinically definite relapsing-remitting MS, she was treated with various MS disease-modifying therapies and eventually began experiencing secondary progression. At age 57 years, she developed an acute longitudinally extensive transverse myelitis and was found to have AQP4 antibodies by cell-based assay. Our analysis of the clinical course, radiographic findings, molecular diagnostic methods, and treatment response characteristics support the hypothesis that our patient most likely had 2 CNS inflammatory disorders: MS, which manifested as a teenager, and neuromyelitis optica spectrum disorder, which evolved in her sixth decade of life. This case emphasizes a key principle in neurology practice, which is to reconsider whether the original working diagnosis remains tenable, especially when confronted with evidence (clinical and/or paraclinical) that raises the possibility of a distinctively different disorder
The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as
the basis for constructing a new radio-selected sample of optically bright
quasars. This is the first radio-selected sample that is competitive in size
with current optically selected quasar surveys. Using only two basic criteria,
radio-optical positional coincidence and optical morphology, quasars and BL
Lacs can be identified with 60% selection efficiency; the efficiency increases
to 70% for objects fainter than magnitude 17. We show that a more sophisticated
selection scheme can predict with better than 85% reliability which candidates
will turn out to be quasars.
This paper presents the second installment of the FIRST Bright Quasar Survey
with a catalog of 636 quasars distributed over 2682 square degrees. The quasar
sample is characterized and all spectra are displayed. The FBQS detects both
radio-loud and radio-quiet quasars out to a redshift z>3. We find a large
population of objects of intermediate radio-loudness; there is no evidence in
our sample for a bimodal distribution of radio characteristics. The sample
includes ~29 broad absorption line quasars, both high and low ionization, and a
number of new objects with remarkable optical spectra.Comment: 41 pages plus 39 gifs which contain all quasar spectra. Accepted for
publication in the Astrophysical Journal Supplement Serie
Cardiac performance, biomarkers and gene expression studies in previously sedentary men participating in half-marathon training
BACKGROUND: The mechanisms through which exercise reduces cardiovascular disease are not fully understood. We used echocardiograms, cardiac biomarkers and gene expression to investigate cardiovascular effects associated with exercise training.
METHODS: Nineteen sedentary men (22-37 years) completed a 17-week half-marathon training program. Serial measurements of resting heart rate, blood pressure, maximum oxygen consumption, lipids, C-reactive protein, cardiac troponin T, echocardiograms and blood for gene expression were obtained from baseline to peak training. Controls included 22 sedentary men who did not exercise.
RESULTS: Among the training group, VO2 max increased from 37.1 to 42.0 ml/kg/min (pâ\u3câ0.001). Significant changes were seen in left ventricular wall thickness and mass, stroke volume, resting heart rate and blood pressure (pâ\u3câ0.001). The control group demonstrated no significant changes. Expression profiling in the training group identified 10 significantly over-expressed and 53 significantly under-expressed loci involved in inflammatory pathways. Dividing the training group into high and low responders based on percent change in VO2 max identified loci that differentiated these two groups at baseline and after training.
CONCLUSION: Intensive exercise training leads to significant increase in cardiac and hemodynamic performance, and significant changes in expression of genes involved in immune and inflammatory response.
The Supercooling of a Nematic Liquid Crystal
We investigate the supercooling of a nematic liquid crystal using fluctuating
non-linear hydrodynamic equations. The Martin-Siggia-Rose formalism is used to
calculate renormalized transport coefficients to one-loop order. Similar
theories for isotropic liquids have shown substantial increases of the
viscosities as the liquid is supercooled or compressed due to feedback from the
density fluctuations which are freezing. We find similar results here for the
longitudinal and various shear viscosities of the nematic. However, the two
viscosities associated with the nematic director motion do not grow in any
dramatic way; i.e.\ there is no apparent freezing of the director modes within
this hydrodynamic formalism. Instead a glassy state of the nematic may arise
from a ``random anisotropy" coupling of the director to the frozen density.Comment: Late
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