2,737 research outputs found
Moduli and periods of simply connected Enriques surfaces
We describe a period map for those simply connected Enriques surfaces in
characteristic 2 whose canonical double cover is K3. The moduli stack for these
surfaces has a Deligne-Mumford quotient that is an open substack of a -bundle over the period space. We also give some general results relating
local and global moduli for algebraic varieties and describe the difference in
their dimensions in terms of the failure of the automorphism group scheme to be
reduced
Observations of deep coral and sponge assemblages in Olympic Coast National Marine Sanctuary, Washington. Cruise Report: NOAA Ship McArthur II Cruise AR06-07/07
From May 22 to June 4, 2006, NOAA scientists led a research cruise using the ROPOS Remotely Operated Vehicle (ROV) to conduct a series of dives at targeted sites in the
Olympic Coast National Marine Sanctuary (OCNMS) with the goal of documenting deep coral and sponge communities. Dive sites were selected from areas for which OCNMS had side scan sonar data indicating the presence of hard or complex substrate. The team completed 11 dives in sanctuary waters ranging from six to 52 hours in length, at depths ranging from 100 to 650 meters. Transect surveys were completed at 15 pre-selected sites, with additional observations made at five other sites. The survey locations included sites both inside and outside the Essential Fish Habitat (EFH) Conservation Area, known as Olympic 2, established by the Pacific Fishery Management Council, enacted on June 12, 2006. Bottom trawling is prohibited in the Olympic 2 Conservation Area for nontribal fishermen. The Conservation Area covers 159.4 square nautical miles or about 15
percent of the sanctuary. Several species of corals and sponges were documented at 14 of the 15 sites surveyed, at sites both inside and outside the Conservation Area, including numerous gorgonians and the stony corals Lophelia pertusa and Desmophyllum dianthus, as well as small patches of the reef building sponge Farrea occa. The team also
documented Lophelia sp. and Desmophyllum sp. coral rubble, dead gorgonians, lost fishing gear, and other anthropogenic debris, supporting concerns over potential risks of
environmental disturbances to coral health. (PDF contains 60 pages.
Far-infrared observations of young clusters embedded in the R Coronae Austrinae and RHO Ophiuchi dark clouds
Multicolor far infrared maps in two nearby dark clouds, R Coronae Austrinae and rho Ophiuchi, were made in order to investigate the individual contribution of low mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low mass stars in Cr A and four in rho Oph was detected; their far infrared luminosities range from 2 far infrared luminosities L. up to 40 far infrared luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50% of the star's energy was radiated longward of 20 micrometers. meaningful limits to the far infrared luminosities of an additional eleven association members in Cr A and two in rho Oph were also obtained. The dust optical depth surrounding the star R Cr A appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of the results for the cloud energetics and star formation efficiency in these two clouds are discussed
The Optical/Near-IR Colors of Broad Absorption Line Quasars, Including the Candidate Radio-Loud BAL Quasar 1556+3517
A candidate radio-loud broad absorption line quasar (RLBAL) has been reported
by Becker et al. (1997). We present JHK observations of this object and three
other radio-detected BALs taken with the new Michigan-Dartmouth-MIT/Ohio
State/Aladdin IR Camera (MOSAIC) on the KPNO 4-meter. The candidate RLBAL
1556+3517 has B-K=6.63, redder than all but one or two known z>1 quasars. This
strongly suggests the observed continuum of this quasar is reddened by dust.
Even when this extreme reddening is taken into account 1556+3517 is still
probably radio-loud, although near-IR spectroscopy to measure its Balmer
decrement will be needed to verify this. In addition, since it is a
flat-spectrum object, VLBI observations to determine the extent (if any) to
which beaming affects our estimate of its radio luminosity will be needed
before 1556+3517 can be unequivocally declared a radio-loud BAL. We also use
our data and data from the literature to show that optically selected BALs as a
class have B-K colors consistent with the observed distribution for optically
selected quasars as a whole. Thus there is currently no evidence that the
tendency of optically selected BALs to be preferentially radio-intermediate
(Hooper, Francis, & Impey 1993) is due to extinction artificially lowering
estimated BAL optical luminosities. However, as most quasar surveys, both radio
and optical, would be insensitive to a population of reddened radio-quiet BALs,
the existence of a large population of reddened BALs similar to 1556+3517
cannot yet be ruled out.Comment: Accepted to ApJ Letters; 10 pages including 1 figure and 2 tables.
This version somewhat revised from initial submission, with a better figur
Intervention and revision: Expertise and interaction in text mediation
Many EAL (English as an Additional Language) scholars enlist text mediators’ support when faced with the challenges of writing for international publication. However, the contributions these individuals are able to make in improving scientific manuscripts remains unclear, especially when language professionals such as English teachers do this work. In this article, we explore this topic by examining how three mediators employed their very different expertise and brought different processes to bear on the same discussion section of a medical manuscript written by a novice scholar in China. We find that successfully mediated texts are often the result of an interplay between the mediator’s expertise and the relationship between the participants. Our findings contradict those of previous studies that question the role of English teachers in this process and have the potential to inform both text mediation practices and revision studies
Effect of an oil spill on benthic animals in the lower York River, Virginia
Although considerable study has been centered upon intertidal organisms with respect to their response to oil spills, most investigations have been conducted on exposed rocky intertidal habitats (1). Few studies are available which describe the response of benthic animal communities in mid-Atlantic estuaries and particularly in its largest estuary, Chesapeake Bay. This study documents both from field survey data and laboratory bioassay studies the effects of an accidental oil spill on the intertidal benthic communities of the Lower York River, Virginia
Layer by layer - Combining Monads
We develop a method to incrementally construct programming languages. Our
approach is categorical: each layer of the language is described as a monad.
Our method either (i) concretely builds a distributive law between two monads,
i.e. layers of the language, which then provides a monad structure to the
composition of layers, or (ii) identifies precisely the algebraic obstacles to
the existence of a distributive law and gives a best approximant language. The
running example will involve three layers: a basic imperative language enriched
first by adding non-determinism and then probabilistic choice. The first
extension works seamlessly, but the second encounters an obstacle, which
results in a best approximant language structurally very similar to the
probabilistic network specification language ProbNetKAT
Axial Symmetry and Rotation in the SiO Maser Shell of IK Tauri
We observed v=1, J=1-0 43-GHz SiO maser emission toward the Mira variable IK
Tauri (IK Tau) using the Very Long Baseline Array (VLBA). The images resulting
from these observations show that SiO masers form a highly elliptical ring of
emission approximately 58 x 32 mas with an axial ratio of 1.8:1. The major axis
of this elliptical distribution is oriented at position angle of ~59 deg. The
line-of-sight velocity structure of the SiO masers has an apparent axis of
symmetry consistent with the elongation axis of the maser distribution.
Relative to the assumed stellar velocity of 35 km/s, the blue- and red-shifted
masers were found to lie to the northwest and southeast of this symmetry axis
respectively. This velocity structure suggests a NW-SE rotation of the SiO
maser shell with an equatorial velocity, which we determine to be ~3.6 km/s.
Such a NW-SE rotation is in agreement with a circumstellar envelope geometry
invoked to explain previous water and OH maser observations. In this geometry,
water and OH masers are preferentially created in a region of enhanced density
along the NE-SW equator orthogonal to the rotation/polar axis suggested by the
SiO maser velocities.Comment: 17 Pages, 4 figures (2 color); accepted for publication in Ap
Near Infrared Adaptive Optics Imaging of QSO Host Galaxies
We report near-infrared (primarily H-band) adaptive optics (AO) imaging with
the Gemini-N and Subaru Telescopes, of a representative sample of 32 nearby
(z<0.3) QSOs selected from the Palomar-Green (PG) Bright Quasar Survey (BQS),
in order to investigate the properties of the host galaxies. 2D modeling and
visual inspection of the images shows that ~36% of the hosts are ellipticals,
\~39% contain a prominent disk component, and ~25% are of undetermined type.
30% show obvious signs of disturbance. The mean M_H(host) = -24.82 (2.1L_H*),
with a range -23.5 to -26.5 (~0.63 to 10 L_H*). At <L_H*, all hosts have a
dominant disk component, while at >2 L_H* most are ellipticals. "Disturbed"
hosts are found at all M_H(host), while "strongly disturbed" hosts appear to
favor the more luminous hosts. Hosts with prominent disks have less luminous
QSOs, while the most luminous QSOs are almost exclusively in ellipticals or in
mergers (which presumably shortly will be ellipticals). At z<0.13, where our
sample is complete at B-band, we find no clear correlation between M_B(QSO) and
M_H(host). However, at z>0.15, the more luminous QSOs (M_B<-24.7), and 4/5 of
the radio-loud QSOs, have the most luminous H-band hosts (>7L_H*), most of
which are ellipticals. Finally, we find a strong correlation between the
"infrared-excess", L_IR/L_BB, of QSOs with host type and degree of disturbance.
Disturbed and strongly disturbed hosts and hosts with dominant disks have
L_IR/L_BB twice that of non-disturbed and elliptical hosts, respectively. QSOs
with "disturbed" and "strongly-disturbed" hosts are also found to have
morphologies and mid/far-infrared colors that are similar to what is found for
"warm" ultraluminous infrared galaxies, providing further evidence for a
possible evolutionary connection between both classes of objects.Comment: 80 pages, accepted for publication in ApJ Supp
Globalisation, neo-liberalism and vocational learning: the case of English further education colleges
Further education (FE) has traditionally been a rather unspectacular activity. Lacking the visibility of schools or the prestige of universities, for the vast majority of its existence FE has had a relatively low profile on the margins of English education. Over recent years this situation has altered significantly and further education has undergone profound change. This paper argues that a combination of related factors – neo-liberalism, globalisation, and dominant discourses of the knowledge economy – has acted in synergy to transform FE into a highly performative and marketised sector. Against this backdrop, further education has been assigned a particular role based upon certain narrow and instrumental understandings of skill, employment and economic competitiveness. The paper argues that, although it has always been predominantly working class in nature, FE is now, more than ever, positioned firmly at the lower end of the institutional hierarchy in the highly class-stratified terrain of English education
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