1,878 research outputs found
Free drifting buoy trajectories in the Gulf Stream system : 1975-1978 : a data report
From 1975 to 1978, thirty-one satellite-tracked free-drifting surface
buoys were launched in the Gulf Stream system. Most of these buoys were
launched in cyclonic rings, as part of an interdisciplinary Gulf Stream ring
experiment, Other buoys were launched in anticyclonic rings and the Gulf
Stream itself; one buoy was launched in a cyclonic Kuroshio ring. The basic
data set consists of buoy trajectories and sea surface temperature and
velocity measurements along trajectories.
The main results consist of a series of 19 buoy trajectories in rings
from which the movement of rings is inferred and a series of 20 buoy trajectories
in the Gulf Stream. Rings frequently coalesced with the Gulf
Stream, and some reformed as modified rings. The trajectories of buoys in
the Stream reveal that at times surface currents are strongly influenced by
topographic features such as seamounts and ridges. Most buoys in the Stream
continued to move eastward until they reached the vicinity of the Grand
Banks (50°W) where they rapidly fanned out, some moving northward, others
eastward across the mid-Atlantic Ridge, still others southward and westward .Prepared for the Office of Naval Research under
Contract N00014-74-C-0262; NR 083-004 and for
the National Science Foundation under Grants
OCE 75-008765 and OCE 77-08045
Comparative Genome-Wide Screening Identifies a Conserved Doxorubicin Repair Network That Is Diploid Specific in Saccharomyces cerevisiae
The chemotherapeutic doxorubicin (DOX) induces DNA double-strand break (DSB) damage. In order to identify conserved genes that mediate DOX resistance, we screened the Saccharomyces cerevisiae diploid deletion collection and identified 376 deletion strains in which exposure to DOX was lethal or severely reduced growth fitness. This diploid screen identified 5-fold more DOX resistance genes than a comparable screen using the isogenic haploid derivative. Since DSB damage is repaired primarily by homologous recombination in yeast, and haploid cells lack an available DNA homolog in G1 and early S phase, this suggests that our diploid screen may have detected the loss of repair functions in G1 or early S phase prior to complete DNA replication. To test this, we compared the relative DOX sensitivity of 30 diploid deletion mutants identified under our screening conditions to their isogenic haploid counterpart, most of which (n = 26) were not detected in the haploid screen. For six mutants (bem1Δ, ctf4Δ, ctk1Δ, hfi1Δ,nup133Δ, tho2Δ) DOX-induced lethality was absent or greatly reduced in the haploid as compared to the isogenic diploid derivative. Moreover, unlike WT, all six diploid mutants displayed severe G1/S phase cell cycle progression defects when exposed to DOX and some were significantly enhanced (ctk1Δ and hfi1Δ) or deficient (tho2Δ) for recombination. Using these and other “THO2-like” hypo-recombinogenic, diploid-specific DOX sensitive mutants (mft1Δ, thp1Δ, thp2Δ) we utilized known genetic/proteomic interactions to construct an interactive functional genomic network which predicted additional DOX resistance genes not detected in the primary screen. Most (76%) of the DOX resistance genes detected in this diploid yeast screen are evolutionarily conserved suggesting the human orthologs are candidates for mediating DOX resistance by impacting on checkpoint and recombination functions in G1 and/or early S phases
Loss of Structural Complexity in Staghorn Coral Rubble Habitats Influences the Density of Damselfish in Dry Tortugas National Park, Florida, USA
An Atlas of Halpha and R Images and Radial Profiles of 63 Bright Virgo Cluster Spiral Galaxies
Narrow-band Halpha and broadband R images and radial profiles are presented
for 63 bright spiral galaxies in the Virgo Cluster. The sample is complete for
Sb-Scd galaxies with B magnitude less than 12 and inclination less than 75
degrees. Isophotal radii, disk scalelengths, concentration parameters, and
integrated fluxes are derived for the sample galaxies.Comment: 46 pages, 8 figures, including 15 pages of atlas images. Higher
resolution postscript versions of the image and radial profile figures are
available at http://www1.union.edu/~koopmanr/preprints.html . Accepted for
publication in Astrophysical Journal Supplement Serie
Gaussian Quantum Information
The science of quantum information has arisen over the last two decades
centered on the manipulation of individual quanta of information, known as
quantum bits or qubits. Quantum computers, quantum cryptography and quantum
teleportation are among the most celebrated ideas that have emerged from this
new field. It was realized later on that using continuous-variable quantum
information carriers, instead of qubits, constitutes an extremely powerful
alternative approach to quantum information processing. This review focuses on
continuous-variable quantum information processes that rely on any combination
of Gaussian states, Gaussian operations, and Gaussian measurements.
Interestingly, such a restriction to the Gaussian realm comes with various
benefits, since on the theoretical side, simple analytical tools are available
and, on the experimental side, optical components effecting Gaussian processes
are readily available in the laboratory. Yet, Gaussian quantum information
processing opens the way to a wide variety of tasks and applications, including
quantum communication, quantum cryptography, quantum computation, quantum
teleportation, and quantum state and channel discrimination. This review
reports on the state of the art in this field, ranging from the basic
theoretical tools and landmark experimental realizations to the most recent
successful developments.Comment: 51 pages, 7 figures, submitted to Reviews of Modern Physic
Learning to Teach About Ideas and Evidence in Science : The Student Teacher as Change Agent
A collaborative curriculum development project was set up to address the lack of good examples of teaching about ideas and evidence and the nature of science encountered by student teachers training to teach in the age range 11-16 in schools in England. Student and teacher-mentor pairs devised, taught and evaluated novel lessons and approaches. The project design required increasing levels of critique through cycles of teaching, evaluation and revision of lessons. Data were gathered from interviews and students' reports to assess the impact of the project on student teachers and to what extent any influences survived when they gained their first teaching posts. A significant outcome was the perception of teaching shifting from the delivery of standard lessons in prescribed ways to endeavours demanding creativity and decision-making. Although school-based factors limited newly qualified teachers' chances to use new lessons and approaches and therefore act as change-agents in schools, the ability to critique curriculum materials and the recognition of the need to create space for professional dialogue were durable gains
Detecting Topology in a Nearly Flat Spherical Universe
When the density parameter is close to unity, the universe has a large
curvature radius independently of its being hyperbolic, flat, or spherical.
Whatever the curvature, the universe may have either a simply connected or a
multiply connected topology. In the flat case, the topology scale is arbitrary,
and there is no a priori reason for this scale to be of the same order as the
size of the observable universe. In the hyperbolic case any nontrivial topology
would almost surely be on a length scale too large to detect. In the spherical
case, by contrast, the topology could easily occur on a detectable scale. The
present paper shows how, in the spherical case, the assumption of a nearly flat
universe simplifies the algorithms for detecting a multiply connected topology,
but also reduces the amount of topology that can be seen. This is of primary
importance for the upcoming cosmic microwave background data analysis.
This article shows that for spherical spaces one may restrict the search to
diametrically opposite pairs of circles in the circles-in-the-sky method and
still detect the cyclic factor in the standard factorization of the holonomy
group. This vastly decreases the algorithm's run time. If the search is widened
to include pairs of candidate circles whose centers are almost opposite and
whose relative twist varies slightly, then the cyclic factor along with a
cyclic subgroup of the general factor may also be detected. Unfortunately the
full holonomy group is, in general, unobservable in a nearly flat spherical
universe, and so a full 6-parameter search is unnecessary. Crystallographic
methods could also potentially detect the cyclic factor and a cyclic subgroup
of the general factor, but nothing else.Comment: 16 pages, 7 figure
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