24,333 research outputs found
Trident: A three-pronged galaxy survey. I. Lyman alpha emitting galaxies at z~2 in GOODS North
Context. Lyman alpha emitting galaxies (LAEs) are used to probe the distant
universe and are therefore important for galaxy evolution studies and for
providing clues to the nature of the epoch of reionization, but the exact
circumstances under which Lyman alpha escapes a galaxy are still not fully
understood.
Aims. The Trident project is designed to simultaneously examine Lyman alpha,
H-alpha and Lyman Continuum emission from galaxies at redshift z~2, thus
linking together these three aspects of ionising radiation in galaxies. In this
paper, we outline the strategy of this project and examine the properties of
LAEs in the GOODS North field.
Methods. We performed a narrowband LAE survey in GOODS North using existing
and two custom made filters at the Nordic Optical Telescope with MOSCA. We use
complementary broad band archival data in the field to make a careful candidate
selection and perform optical to near-IR SED fitting. We also estimate
far-infrared luminosities by matching our candidates to detections in
Spitzer/MIPS 24{\mu}m and Herschel/PACS catalogs.
Results. We find a total of 25 LAE candidates, probing mainly the bright end
of the LAE luminosity function with L_Ly {\alpha} ~ 1-15e42 erg/s. They display
a range of masses of ~0.5-50e9 M_solar, and average ages from a few tens of Myr
to 1 Gyr when assuming a constant star formation history. The majority of our
candidates also show signs of recent elevated star formation. Three candidates
have counterparts in the GOODS-Herschel far-IR catalogue, with luminosities
consistent with ultra-luminous infrared galaxies (ULIRGs).
Conclusions. The wide range of parameters derived from our SED fitting, as
well as part of our sample being detected as ULIRGs, seems to indicate that at
these Lyman alpha luminosities, LAEs do not necessarily have to be young
dwarfs, and that a lack of dust is not required for Lyman alpha to escape.Comment: 16 pages, 12 figures. Accepted version for publication in A&
VLT/MUSE view of the highly ionized outflow cones in the nearby starburst ESO338-IG04
The Ly line is an important diagnostic for star formation at high
redshift, but interpreting its flux and line profile is difficult because of
the resonance nature of Ly. Trends between the escape of Ly
photons and dust and properties of the interstellar medium (ISM) have been
found, but detailed comparisons between Ly emission and the properties
of the gas in local high-redshift analogs are vital for understanding the
relation between Ly emission and galaxy properties. For the first time,
we can directly infer the properties of the ionized gas at the same location
and similar spatial scales of the extended Ly halo around ESO 338-IG04.
We obtained VLT/MUSE integral field spectra. We used ionization parameter
mapping of the [SII]/[OIII] line ratio and the kinematics of H to study
the ionization state and kinematics of the ISM of ESO338-IG04. The velocity map
reveals two outflows. The entire central area of the galaxy is highly ionized
by photons leaking from the HII regions around the youngest star clusters.
Three highly ionized cones have been identified, of which one is associated
with an outflow. We propose a scenario where the outflows are created by
mechanical feedback of the older clusters, while the highly ionized gas is
caused by the hard ionizing photons emitted by the youngest clusters. A
comparison with the Ly map shows that the (approximately bipolar)
asymmetries observed in the Ly emission are consistent with the base of
the outflows detected in H. No clear correlation with the ionization
cones is found. The mechanical and ionization feedback of star clusters
significantly changes the state of the ISM by creating ionized cones and
outflows. The comparison with Ly suggests that especially the outflows
could facilitate the escape of Ly photons [Abridged].Comment: Accepted for publication in A&A Letters, 4 pages, 2 figure
Inadequacy of Scaling Arguments for Neutrino Cross Sections
The problem with the use of scaling arguments for simultaneous studies of
different weak interaction processes is discussed. When different neutrino
scattering cross sections involving quite different momentum transfers are
being compared it difficult to define a meaningful single scaling factor to
renormalize calculated cross sections. It has been suggested that the use of
such scaling can be used to estimate high energy neutrino cross sections from
low energy neutrino cross sections. This argument has lead to questions on the
consistency of the magnitude of the LSND muon neutrino cross sections on
C relative to other lower energy weak processes. The issue is revisited
here and from inspection of the structure of the form factors involved it is
seen that the problem arises from a poor description of the transition form
factors at high momentum transfer. When wave functions that reproduce the
transverse magnetic inelastic (e,e') scattering form factor for the 15.11 MeV
state in C are used there is no longer a need for scaling the axial
current, and the different weak interactions rates involving the T=1 1
triplet in mass 12 are consistent with one another.Comment: 3 pages, 1 figur
Programmed schedule holds for improving launch vehicle holds
Baseline definition and system optimization are used for the analysis of programmed holds developed through prelaunch system analysis. Identification of design specifications for ground support equipment and maintenance concepts, and design specifications are used to describe the functional utilization of the overall flow process
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Towards omnicompetence: the need for effective school-based preparation for primary headship
Teachers are entering deputy headship and then deciding not to become headteachers. This is a double problem for the profession. Firstly, potential headteachers are being lost to that role, and secondly, career deputies block the route to headship and prevent ambitious deputies from getting that essential management experience that will effectively prepare them for headship.
In Bromley, where this study was carried out, some deputies are getting good advice and support from their headteachers, are given real leadership development opportunities and are going on to become effective headteachers. However, some deputies are given low grade tasks and do not receive the support and encouragement from their headteachers that will lead them towards headship. Finally, there are some deputies who, although in a supportive environment, have decided that headship is not for them.
Initially, a short survey of all primary schools in Bromley was conducted to gain an overall picture of deputy headship in Bromley. All schools were contacted to find out whether the deputy at the school was interested in becoming a headteacher at some stage in the future.
During a period of twelve weeks, eleven primary headteachers were interviewed together with a senior Local Authority adviser. The aim of the work was to gain a picture of the state of deputy headship in one London Borough and establish what experiences and opportunities were given to deputy headteacher to prepare them for headship.
This inquiry found that the majority of deputies in Bromley did not want to be headteachers and that their preparation experiences differs greatly from school to school. The study suggests that deputies should be given the opportunities and experiences that will prepare them for headship. Information from the literature review, the survey and interviews are analysed to construct a model for effective preparation for headship and to make recommendations for improved practice
Super star cluster feedback driving ionization, shocks and outflows in the halo of the nearby starburst ESO 338-IG04
Stellar feedback strongly affects the interstellar medium (ISM) of galaxies.
Stellar feedback in the first galaxies likely plays a major role in enabling
the escape of LyC photons, which contribute to the re-ionization of the
Universe. Nearby starburst galaxies serve as local analogues allowing for a
spatially resolved assessment of the feedback processes in these galaxies. We
characterize the feedback effects from the star clusters in the local
high-redshift analogue ESO 338-IG04 on the ISM and compare the results with the
properties of the most massive clusters. We use high quality VLT/MUSE optical
integral field data to derive the physical properties of the ISM such as
ionization, density, shocks, and perform new fitting of the spectral energy
distributions of the brightest clusters in ESO 338-IG04 from HST imaging. ESO
338-IG04 has a large ionized halo which we detect to a distance of 9 kpc. We
identify 4 Wolf-Rayet (WR) clusters based on the blue and red WR bump. We
follow previously identified ionization cones and find that the ionization of
the halo increases with distance. Analysis of the galaxy kinematics shows two
complex outflows driven by the numerous young clusters in the galaxy. We find a
ring of shocked emission traced by an enhanced [OI]/H ratio surrounding
the starburst and at the end of the outflow. Finally we detect nitrogen
enriched gas associated with the outflow, likely caused by the WR stars in the
massive star clusters. Photo-ionization dominates the central starburst and
sets the ionization structure of the entire halo, resulting in a density
bounded halo, facilitating the escape of LyC photons. Outside the central
starburst, shocks triggered by an expanding super bubble become important. The
shocks at the end of the outflow suggest interaction between the hot outflowing
material and the more quiescent halo gas.Comment: Accepted for publication in Astronomy and Astrophysics, 22 pages, 15
figure
Reconstruction of eolian bed forms and paleocurrents from cross-bedded strata at Victoria Crater, Meridiani Planum, Mars
Outcrop exposures imaged by the Opportunity rover at Victoria Crater, a 750 m diameter crater in Meridiani Planum, are used to delineate sedimentary structures and further develop a dune-interdune depositional model for the region. The stratigraphy at Victoria Crater, observed during Opportunity's partial traverse of its rim, includes the best examples of meter-scale eolian cross bedding observed on Mars to date. The Cape St. Mary promontory, located at the southern end of the rim traverse, is characterized by meter-scale sets of trough cross bedding, suggesting northward migrating sinuous-crested bed forms. Cape St. Vincent, which is located at the opposite end of the traverse, shows tabular-planar stratification indicative of climbing bed forms with meter- to decameter-scale dune heights migrating southward. Promontories located between Cape St. Mary and Cape St. Vincent contain superposed stratigraphic units with northward and southward dipping beds separated by outcrop-scale bounding surfaces. These bounding surfaces are interpreted to be either reactivation and/or superposition surfaces in a complex erg sea. Any depositional model used to explain the bedding must conform to reversing northward and southward paleomigration directions and include multiple scales of bed forms. In addition to stratified outcrop, a bright diagenetic band is observed to overprint bedding and to lie on an equipotential parallel to the preimpact surface. Meter-scale cross bedding at Victoria Crater is similar to terrestrial eolian deposits and is interpreted as a dry dune field, comparable to Jurassic age eolian deposits in the western United States
Engineering Electromagnetic Properties of Periodic Nanostructures Using Electrostatic Resonances
Electromagnetic properties of periodic two-dimensional sub-wavelength
structures consisting of closely-packed inclusions of materials with negative
dielectric permittivity in a dielectric host with positive
can be engineered using the concept of multiple electrostatic
resonances. Fully electromagnetic solutions of Maxwell's equations reveal
multiple wave propagation bands, with the wavelengths much longer than the
nanostructure period. It is shown that some of these bands are described using
the quasi-static theory of the effective dielectric permittivity
, and are independent of the nanostructure period. Those bands
exhibit multiple cutoffs and resonances which are found to be related to each
other through a duality condition. An additional propagation band characterized
by a negative magnetic permeability develops when a magnetic moment is induced
in a given nano-particle by its neighbors. Imaging with sub-wavelength
resolution in that band is demonstrated
Talactoferrin Immunotherapy in Metastatic Renal Cell Carcinoma: A Case Series of Four Long-Term Survivors
Talactoferrin alfa (also known as recombinant human lactoferrin, rhLF) is a novel immunomodulatory protein that has previously demonstrated anti-tumor properties in animal models. Following a successful phase I trial, it was administered orally to patients with metastatic renal cell carcinoma (RCC) in a phase II trial conducted at the Michael E. DeBakey Veterans Affairs Medical Center in Houston, Texas, among other sites. We report a case series of 4 patients treated at our institution with very encouraging progression-free survivals, all exceeding 30 months, in order to suggest that this agent merits further study. These four patients with radiographically progressive metastatic RCC received single-agent oral talactoferrin in daily doses of 9 grams, given in cycles of 2 weeks on/2 weeks off, until evidence of toxicity or disease progression. Given the small sample size and the heterogenous tumor biology of RCC, tumor growth rate was used as a primary endpoint so that each patient could serve as their own control. The agent's effectiveness was then determined through radiographic tracking of the tumors before, during, and after treatment, with use of the Response Evaluation Criteria in Solid Tumors (RECIST) protocol to follow target lesions. The results showed that the drug was well tolerated, with no occurrence of talactoferrin-related grade 3 or 4 adverse events or laboratory anomalies by NCI-CTEP criteria. The four patients described in the case series demonstrated very encouraging progression-free survivals, all exceeding 30 months. We conclude that decreased tumor growth rate may correlate with increased progression-free survival. Talactoferrin is a promising, well-tolerated agent whose clinical benefits should be evaluated in a randomized phase III study with a placebo control arm
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