920 research outputs found
Missing GRB host galaxies in deep mid-infrared observations: implications on the use of GRBs as star formation tracers
We report on the first mid-infrared observations of 16 GRB host galaxies performed with the Spitzer Space Telescope, and investigate the presence of evolved stellar populations and dust-enshrouded star-forming activity associated with GRBs. Only a very small fraction of our sample is detected by Spitzer, which is not consistent with recent works suggesting the presence of a GRB host population dominated by massive and strongly-starbursting galaxies (SFR >~ 100M[sun]yr^–1). Should the GRB hosts be representative of star-forming galaxies at high redshift, models of galaxy evolution indicate that >~ 50% of GRB hosts would be easily detected at the depth of our mid-infrared observations. Unless our sample suffers from a strong observational bias which remains to be understood, we infer in this context that the GRBs identified with the current techniques can not be directly used as unbiased probes of the global and integrated star formation history of the Universe
Assessing the Promise of a Supplemental Reading Intervention for At-Risk First Grade Students in a Public School Setting
In this exploratory quasi-experimental case study, we assessed the promise of a yearlong supplemental reading intervention with a small pilot group of at-risk first grade readers in an elementary school setting. Using standardized measures of reading proficiency, we found that after 47 hours of one-on-one tutoring instruction, students read significantly more proficiently than did non-tutored students in a matched group of first grade peers in the same school. These results are encouraging in light of literacy research documenting the impact of one-on-one tutoring by qualified tutors of at-risk early grade readers. We used lessons learned from this pilot study to help inform and direct the necessary revisions and refinements of future reading interventions with the goal of building the school’s capacity to support the literacy development of at-risk readers so that they can catch up with their typically developing peers
Probing the cosmic star formation using long Gamma-Ray Bursts: New constraints from the Spitzer Space Telescope
We report on IRAC-4.5mic, IRAC-8.0mic and MIPS-24mic deep observations of 16
Gamma-Ray Burst (GRBs) host galaxies performed with the Spitzer Space
Telescope, and we investigate in the thermal infrared the presence of evolved
stellar populations and dust-enshrouded star-forming activity associated with
these objects. Our sample is derived from GRBs that were identified with
sub-arcsec localization between 1997 and 2001, and only a very small fraction
(~20%) of the targeted sources is detected down to f_4.5mic ~3.5microJy and
f_24mic ~85microJy (3sigma). This likely argues against a population dominated
by massive and strongly-starbursting (i.e., SFR > ~100 Msol/yr) galaxies as it
has been recently suggested from submillimeter/radio and optical studies of
similarly-selected GRB hosts. Furthermore we find evidence that some GRBs do
not occur in the most infrared-luminous regions -- hence the most actively
star-forming environments -- of their host galaxies. Should the GRB hosts be
representative of all star-forming galaxies at high redshift, models of
infrared galaxy evolution indicate that > ~50% of GRB hosts should have f_24mic
> ~100microJy. Unless the identification of GRBs prior to 2001 was prone to
strong selection effects biasing our sample against dusty galaxies, we infer in
this context that the GRBs identified with the current techniques can not be
directly used as unbiased probes of the global and integrated star formation
history of the Universe.Comment: ApJ in press, 23 pages, 8 figures (scheduled for the ApJ 10 May 2006,
v642 2 issue). Full resolution available at
http://perceval.as.arizona.edu/~elefloch/Publis/ms_grb_spitzer.pd
Inelastic x-ray scattering investigations of lattice dynamics in SmFeAsOF superconductors
We report measurements of the phonon density of states as measured with
inelastic x-ray scattering in SmFeAsOF powders. An unexpected
strong renormalization of phonon branches around 23 meV is observed as fluorine
is substituted for oxygen. Phonon dispersion measurements on
SmFeAsOF single crystals allow us to identify the 21 meV A
in-phase (Sm,As) and the 26 meV B (Fe,O) modes to be responsible for
this renormalization, and may reveal unusual electron-phonon coupling through
the spin channel in iron-based superconductors.Comment: 4 pages, 3 figures, submitted for SNS2010 conference proceeding
Direct observation of molecular cooperativity near the glass transition
We describe direct observations of molecular cooperativity near the glass
transition in poly-vinyl-acetate (PVAc), through nanometer-scale probing of
dielectric fluctuations. Molecular clusters switched spontaneously between two
to four distinct configurations, producing complex random-telegraph-signals
(RTS). Analysis of the RTS and their power spectra shows that individual
clusters exhibit both transient dynamical heterogeneity and non-exponential
kinetics.Comment: 14 pages pdf, need Acrobat Reade
Stack-and-Delay: a new codebook pattern for music generation
In language modeling based music generation, a generated waveform is
represented by a sequence of hierarchical token stacks that can be decoded
either in an auto-regressive manner or in parallel, depending on the codebook
patterns. In particular, flattening the codebooks represents the highest
quality decoding strategy, while being notoriously slow. To this end, we
propose a novel stack-and-delay style of decoding strategy to improve upon the
flat pattern decoding where generation speed is four times faster as opposed to
vanilla flat decoding. This brings the inference time close to that of the
delay decoding strategy, and allows for faster inference on GPU for small batch
sizes. For the same inference efficiency budget as the delay pattern, we show
that the proposed approach performs better in objective evaluations, almost
closing the gap with the flat pattern in terms of quality. The results are
corroborated by subjective evaluations which show that samples generated by the
new model are slightly more often preferred to samples generated by the
competing model given the same text prompts
Enhance audio generation controllability through representation similarity regularization
This paper presents an innovative approach to enhance control over audio
generation by emphasizing the alignment between audio and text representations
during model training. In the context of language model-based audio generation,
the model leverages input from both textual and audio token representations to
predict subsequent audio tokens. However, the current configuration lacks
explicit regularization to ensure the alignment between the chosen text
representation and the language model's predictions. Our proposal involves the
incorporation of audio and text representation regularization, particularly
during the classifier-free guidance (CFG) phase, where the text condition is
excluded from cross attention during language model training. The aim of this
proposed representation regularization is to minimize discrepancies in audio
and text similarity compared to other samples within the same training batch.
Experimental results on both music and audio generation tasks demonstrate that
our proposed methods lead to improvements in objective metrics for both audio
and music generation, as well as an enhancement in the human perception for
audio generation.Comment: 5 page
Genetic Improvement of Software (Dagstuhl Seminar 18052)
We document the program and the immediate outcomes of Dagstuhl Seminar 18052 “Genetic
Improvement of Software”. The seminar brought together researchers in Genetic Improvement
(GI) and related areas of software engineering to investigate what is achievable with current technology and the current impediments to progress and how GI can affect the software development
process. Several talks covered the state-of-the-art and work in progress. Seven emergent topics
have been identified ranging from the nature of the GI search space through benchmarking and
practical applications. The seminar has already resulted in multiple research paper publications.
Four by participants of the seminar will be presented at the GI workshop co-located with the
top conference in software engineering - ICSE. Several researchers started new collaborations,
results of which we hope to see in the near future
Computation of Electrostatic Field near Three-Dimensional Corners and Edges
Theoretically, the electric field becomes infinite at corners of two and
three dimensions and edges of three dimensions. Conventional finite-element and
boundary element methods do not yield satisfactory results at close proximity
to these singular locations. In this paper, we describe the application of a
fast and accurate BEM solver (which usesexact analytic expressions to compute
the effect of source distributions on flatsurfaces) to compute the electric
field near three-dimensional corners and edges. Results have been obtained for
distances as close as 1 near the corner/edge and good agreement has been
observed between the present results and existing analytical solutions.Comment: Presented in International Conference on Computational and
Experimental Engineering and Sciences held at IIT Madras, Chennai, India,
during 1-6 December, 200
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