1,605 research outputs found
Cosmology-Independent Distance Moduli of 42 Gamma-Ray Bursts between Redshift of 1.44 and 6.60
This report is an update and extension of our paper accepted for publication
in ApJ (arXiv:0802.4262). Since objects at the same redshift should have the
same luminosity distance and the distance moduli of type Ia supernovae (SNe Ia)
obtained directly from observations are completely cosmology independent, we
obtain the distance modulus of a gamma-ray burst (GRB) at a given redshift by
interpolating or iterating from the Hubble diagram of SNe Ia. Then we calibrate
five GRB relations without assuming a particular cosmological model, from
different regression methods, and construct the GRB Hubble diagram to constrain
cosmological parameters. Based upon these relations we list the
cosmology-independent distance moduli of 42 GRBs between redshift of 1.44 and
6.60, with the 1- uncertainties of 1-3%.Comment: 6 pages, 2 figures, 3 tables. To appear in the proceedings of "2008
Nanjing GRB conference", Nanjing, 23-27 June 200
Electronic Tuning of Mixed QuinoidalâAromatic Conjugated Polyelectrolytes: Direct Ionic Substitution on Polymer MainâChains
The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron-accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para-azaquinodimethane (AQM) core gives rise to a strongly electron-accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low-lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30â
eV in small molecules down to 1.22â
eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor-acceptor strategy with the bond-length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy
Numerical and experimental investigation of viscous pressure forming (VPF) process for metal bellows
The significance of slab for structural response under travelling fires
The role of âtravelling firesâ is to ensure the robustness of structural design with large compartments under realistic fires, having a fire plume at the near-field, and a hot smoke layer preheating the ceiling at the farfield. Once the fire travels, the near-field has a leading edge representing the fire spread, and a trailing edge representing the burnout of the fuel. Though well understood by its definition, the mainstream of efforts on travelling fires for structural response is limited to 2D finite element modelling (FEM). This paper aims to identify the importance of slab inclusion with a 3D FEM structural model for steel-composite structures under travelling fires, with a special emphasis on the significance of ignoring the slab structural capacity contribution from a 2D simplified structural model. The role of fire protection scheme for 2D model against the 3D model on numerical predictions was also explored. It was found that the structural load path, and the potential structural failure mechanisms could be fundamentally different between the 3D model and the 2D model, i.e., with or without slabs. Although the 2D model tends to predict larger deflections (i.e. more conservative) than the 3D model, it could also significantly underestimate the large internal forces from the beams, which might overlook the connections failure under travelling fires. Further, due to the simplification of the 2D model omitting the significant stiffness contribution from the slab, the effect of the fire protection is likely to be amplified. It may be misleading for the performance-based structural fire design under different travelling fire scenarios. Hence, the 3D model is likely to be considered as necessary and feasible for structural fire analysis for travelling fires as a complement to the 2D model approach
Antennal Morphology and Sexual Dimorphism of Antennal Sensilla in Callitettix versicolor (Fabricius) (Hemiptera: Cercopidae)
The rice spittlebug Callitettix versicolor (Fabricius) is an important pest of rice and maize in
South Asia and causes severe economic damage. To provide background information for chemical
ecology studies, the fine morphology of antennae and the types and distribution of the sensilla on the
male and female antennae of Callitettix versicolor (Fabricius) are investigated by means of scanning
electron microscopy (SEM). Results show that the antenna is filiform and composed of three segments:
a scape, a pedicel, and a flagellum. The female antennae are slightly shorter than the male antennae.
In both sexes, four types and nine subtypes of sensilla were observed: sensilla basiconica (SB1, SB2),
sensilla campaniformia (SCa1, SCa2 and SCa3), sensilla coeloconica (SCo1, SCo2 and SCo3) and
sensilla trichodea (ST). In addition, sensilla coeloconica (SCo1) are observed on the membrane of the
top of the pedicel in Cercopidae for the first time. Sexual dimorphism mainly occurs in variation in
the number of sensilla coeloconica (SCo2, SCo3) on the bulb-shaped portion of the flagellum and in
the shape of sensilla basiconica (SB2). There are significantly more sensilla coeloconica in males than
in females. The external structure and distribution of these sensilla are compared to those of other
cercopids and possible functions of the antennal sensilla are discussed
mixing effects on charmonium and meson decays
We include the meson into the -- mixing formalism
constructed in our previous work, where represents the pseudoscalar
gluball. The mixing angles in this tetramixing matrix are constrained by
theoretical and experimental implications from relevant hadronic processes.
Especially, the angle between and is found to be about
from the measured decay widths of the meson. The pseudoscalar glueball
mass , the pseudoscalar densities and the U(1) anomaly
matrix elements associated with the mixed states are solved from the anomalous
Ward identities. The solution GeV obtained from the
-- mixing is confirmed, while grows to above the pion
mass, and thus increases perturbative QCD predictions for the branching ratios
. We then analyze the -mixing effects on charmonium
magnetic dipole transitions, and on the branching
ratios and CP asymmetries, which further improve the consistency between
theoretical predictions and data. A predominant observation is that the
mixing enhances the perturbative QCD predictions for
by 18%, but does not alter those for . The puzzle due to the
large data is then resolved.Comment: 12 pages, version to appear in PR
Extended Emission of Short Gamma-Ray Bursts
Preliminary results of our analysis on the extended emission of short/medium
duration GRBs observed with Swift/BAT are presented. The Bayesian blocks
algorithm is used to analyze the burst durations and the temporal structure of
the lightcurves in different energy bands. We show here the results of three
bursts (GRBs 050724, 061006 and 070714B) that have a prominent soft extended
emission component in our sample. The extended emission of these bursts is a
continuous, flickering-liked component, lasting seconds post the GRB
trigger at 15-25 keV bands. Without considering this component, the three
bursts are classified as short GRBs, with seconds. GRB 060614
has an emission component similar to the extended emission, but this component
has pulse-liked structure, possibly indicating that this emission component is
different from that observed in GRBs 050724, 061006, and 070714B. Further
analysis on the spectral evolution behavior of the extended emission component
is on going.Comment: 2008 Nanjing GRB Conferenc
Decoupling Zero-Shot Semantic Segmentation
Zero-shot semantic segmentation (ZS3) aims to segment the novel categories
that have not been seen in the training. Existing works formulate ZS3 as a
pixel-level zero-shot classification problem, and transfer semantic knowledge
from seen classes to unseen ones with the help of language models pre-trained
only with texts. While simple, the pixel-level ZS3 formulation shows the
limited capability to integrate vision-language models that are often
pre-trained with image-text pairs and currently demonstrate great potential for
vision tasks. Inspired by the observation that humans often perform
segment-level semantic labeling, we propose to decouple the ZS3 into two
sub-tasks: 1) a class-agnostic grouping task to group the pixels into segments.
2) a zero-shot classification task on segments. The former sub-task does not
involve category information and can be directly transferred to group pixels
for unseen classes. The latter subtask performs at segment-level and provides a
natural way to leverage large-scale vision-language models pre-trained with
image-text pairs (e.g. CLIP) for ZS3. Based on the decoupling formulation, we
propose a simple and effective zero-shot semantic segmentation model, called
ZegFormer, which outperforms the previous methods on ZS3 standard benchmarks by
large margins, e.g., 35 points on the PASCAL VOC and 3 points on the COCO-Stuff
in terms of mIoU for unseen classes. Code will be released at
https://github.com/dingjiansw101/ZegFormer.Comment: 14 pages, 8 figure
Adversarial Preference Optimization
Human preference alignment is a crucial training step to improve the
interaction quality of large language models (LLMs). Existing aligning methods
depend on manually annotated preference data to guide the LLM optimization
directions. However, in practice, continuously updating LLMs raises a
distribution gap between model-generated samples and human-preferred responses,
which hinders model fine-tuning efficiency. To mitigate this issue, previous
methods require additional preference annotation on generated samples to adapt
the shifted distribution, which consumes a large amount of annotation
resources. Targeting more efficient human preference optimization, we propose
an adversarial preference optimization (APO) framework, where the LLM agent and
the preference model update alternatively via a min-max game. Without
additional annotation, our APO method can make a self-adaption to the
generation distribution gap through the adversarial learning process. In
experiments, we empirically verify the effectiveness of APO in improving LLM's
helpfulness and harmlessness compared with rejection sampling baselines.Comment: In proces
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