We report on follow-up observations of the gamma-ray burst GRB 060927 using the robotic ROTSE-IIIa telescope and a suite of larger aperture ground-based telescopes. An optical afterglow was detected ...20 s after the burst, the earliest rest-frame detection of optical emission from any GRB. Spectroscopy performed with the VLT about 13 hr after the trigger shows a continuum break at lambda approximately 8070 AA, produced by neutral hydrogen absorption at unk approximately 5.6. We also detect an absorption line at 8158 AA, which we interpret as Si II lambda 1260 at unk = 5.467. Hence, GRB 060927 is the second most distant GRB with a spectroscopically measured redshift. The shape of the red wing of the spectral break can be fitted by a damped Lya profile with a column density with log(N sub(H)/cm super(-2)) = 22.50 plus or minus 0.15. We discuss the implications of this work for the use of GRBs as probes of the end of the dark ages and draw three main conclusions: (1) GRB afterglows originating from unk unk unk should be relatively easy to detect from the ground, but rapid near-infrared monitoring is necessary to ensure that they are found; (2) the presence of large H I column densities in some GRB host galaxies at unk > 5 makes the use of GRBs to probe the reionization epoch via spectroscopy of the red damping wing challenging; and (3) GRBs appear crucial to locate typical star-forming galaxies at unk > 5, and therefore the type of galaxies responsible for the reionization of the universe.
A
bstract
Single top-quark production in association with a
Z
boson, where the
Z
boson decays to a pair of charged leptons, is measured in the trilepton channel. The proton-proton collision data ...collected by the ATLAS experiment from 2015 to 2018 at a centre-of-mass energy of 13 TeV are used, corresponding to an integrated luminosity of 139 fb
−
1
. Events containing three isolated charged leptons (electrons or muons) and two or three jets, one of which is identified as containing a
b
-hadron, are selected. The main backgrounds are from
t
t
¯
Z
and diboson production. Neural networks are used to improve the background rejection and extract the signal. The measured cross-section for
t
ℓ
+
ℓ
−
q
production, including non-resonant dilepton pairs with
m
ℓ
+
ℓ
−
>
30 GeV, is 97
±
13 (stat.)
±
7 (syst.) fb, consistent with the Standard Model prediction.
Purpose: Following adequate therapy, excellent long-term survival rates can be achieved for patients with optic pathway gliomas. Therefore, avoidance of treatment-related functional long-term ...sequelae is of utmost importance. Optimized sparing of normal tissue is of primary concern in the development of new treatment modalities. The present study compares proton radiation therapy (PRT) with a three-dimensional (3D)-planned multiport photon and a lateral beam photon technique for localized and extensive optic pathway tumors.
Methods and Materials: Between February 1992 and November 1997, seven children with optic pathway gliomas underwent PRT. For this study, we computed proton, 3D photon, and lateral photon plans based on the same CT data sets, and using the same treatment planning software for all plans. Radiation exposure for normal tissue and discrete organs at risk was quantified based on dose-volume histograms.
Results: Gross tumor volume (GTV) ranged from 3.9 cm
3 to 127.2 cm
3. Conformity index (relation of encompassing isodose to GTV volume) was 2.3 for protons, 2.9 for 3D photons, and 7.3 for lateral photons. The relative increase of normal tissue (NT) encompassed at several isodose levels in relation to NT encompassed by the 95% proton isodose volume was computed. Relative NT volume of proton plan isodoses at the 95%, 90%, 80%, 50%, and 25% isodose level increased from 1 to 1.6, 2.8, 6.4, to a maximum of 13.3. Relative volumes for 3D photons were 1.6, 2.4, 3.8, 11.5, and 34.8. Lateral plan relative values were 6, 8.3, 11.5, 19.2, and 26.8. Analysis for small (< 20 cm
3) and larger (> 80 cm
3) tumors showed that protons encompassed the smallest volumes of NT at all isodose levels. Comparable conformity and high-dose gradient were achieved for proton and 3D photon plans in small tumors. However, with increasing tumor volume and complexity, differences became larger. At the 50% isodose level, 3D photons were superior to lateral photons for small tumors; this advantage was equalized for larger tumors. At the lowest isodose level, 3D photons encompassed the highest amount of NT. Analysis of organs at risk showed that PRT reduced doses to the contralateral optic nerve by 47% and 77% compared to 3D photons and lateral photons, respectively. Reductions were also seen for the chiasm (11% and 16%) and pituitary gland (13% and 16%), with differences at clinically relevant tolerance levels. Furthermore, reduced dose exposure of both temporal lobes (sparing 39% and 54%) and frontal lobes was achieved with PRT.
Conclusion: PRT offered a high degree of conformity to target volumes and steep dose gradients, thus leading to substantial normal tissue sparing in high- and low-dose areas. It is expected that this will result in decreased long-term toxicity in the maturing child. Advantages of proton versus 3D photon plans became increasingly apparent with increasing target size and tumor complexity. Even in small tumors, conformity of 3D photon irradiation came at the expense of a larger amount of NT receiving moderate to low radiation doses. Lateral photons resulted in inferior dose distribution with high radiation exposure of clinically relevant normal tissues.
Structural and functional characterization of integrative cartilage repair in controlled model systems can play a key role in the development of innovative strategies to improve the long-term outcome ...of many cartilage repair procedures. In this work, we first developed a method to reproducibly generate geometrically defined disk/ring cartilage composites and to remove outgrown fibrous layers which can encapsulate cartilaginous tissues during culture. We then used the model system to test the hypothesis that such fibrous layers lead to an overestimation of biomechanical parameters of integration at the disk/ring interface. Transmission electron microscopy images of the composites after 6 weeks of culture indicated that collagen fibrils in the fibrous tissue layer were well integrated into the collagen network of the cartilage disk and ring, whereas molecular bridging between opposing disk/ring cartilage surfaces was less pronounced and restricted to regions with narrow interfacial regions (< 2
μm). Stress–strain profiles generated from mechanical push-out tests for composites with the layers removed displayed a single and distinct peak, whereas profiles for composites with the layers left intact consisted of multiple superimposed peaks. As compared to composites with removed layers, composites with intact layers had significantly higher adhesive strengths (161±9 vs. 71±11
kPa) and adhesion energies (15.0±0.7 vs. 2.7±0.4
mJ/mm
2). By combining structural and functional analyses, we demonstrated that the outgrowing tissue formed during in vitro culture of cartilaginous specimens should be eliminated in order to reliably quantify biomechanical parameters related to integrative cartilage repair.
A
bstract
A search for a chargino-neutralino pair decaying via the 125 GeV Higgs boson into photons is presented. The study is based on the data collected between 2015 and 2018 with the ATLAS ...detector at the LHC, corresponding to an integrated luminosity of 139 fb
−
1
of
pp
collisions at a centre-of-mass energy of 13 TeV. No significant excess over the expected background is observed. Upper limits at 95% confidence level for a massless
χ
˜
1
0
are set on several electroweakino production cross-sections and the visible cross-section for beyond the Standard Model processes. In the context of simplified supersymmetric models, 95% confidence-level limits of up to 310 GeV in
m
χ
˜
1
±
/
χ
˜
2
0
, where
m
χ
˜
1
0
= 0
.
5 GeV, are set. Limits at 95% confidence level are also set on the
χ
˜
1
±
χ
˜
2
0
cross-section in the mass plane of
m
χ
˜
1
±
/
χ
˜
2
0
and
m
χ
˜
1
0
, and on scenarios with gravitino as the lightest supersymmetric particle. Upper limits at the 95% confidence-level are set on the higgsino production cross-section. Higgsino masses below 380 GeV are excluded for the case of the higgsino fully decaying into a Higgs boson and a gravitino.
The ROTSE-IIIc telescope at the HESS site, Namibia, obtained the earliest detection of optical emission from a gamma-ray burst (GRB), beginning only 21.8 s from the onset of Swift GRB 050801. The ...optical light curve does not fade or brighten significantly over the first 6250 s, after which there is an achromatic break and the light curve declines in typical power-law fashion. The Swift XRT also obtained early observations starting at 69 s after the burst onset. The X-ray light curve shows the same features as the optical light curve. These correlated variations in the early optical and X-ray emission imply a common origin in space and time. This behavior is difficult to reconcile with the standard models of early afterglow emission.
We present a high-resolution, high S/N optical spectrum of the afterglow of GRB 051111 obtained with the HIRES spectrograph on the Keck I 10 m telescope. The spectrum exhibits three redshifted ...absorption systems with the highest, at z = 1.54948, arising in the GRB host galaxy. While the Lya feature is outside the range of our spectrum, the high column density of weakly depleted Zn suggests that the host is a damped Lya system with N(H super(I)) > 10 super(21)(Z/Z sub(z)) super(-1). The bulk of the gas (>80%) is confined to a narrow velocity range of || < 30 km s super(-1), exhibiting strong dust depletion of refractory elements such as Fe and Cr. The depletion pattern is similar to that observed in warm disk clouds of the Milky Way. We also detect absorption from all ground-level fine-structure states of Fe II, the first such example in a QSO-DLA system or GRB-absorption spectrum, which indicate conditions that are consistent with the "warm disk" depletion pattern. The absorption profiles of Fe II and Mg II extend over several hundred km s super(-1), with a depletion pattern that more closely resembles that of QSO-DLA systems, suggesting that the sight line to GRB 051111 probes the halo of the host galaxy in addition to the dense disk. Thus, detailed diagnostics of the interstellar medium of GRB host galaxies continue to provide insight into regions that are generally missed in quasar surveys.
We present the unfiltered ROTSE-III light curve of the optical transient associated with GRB 050319 beginning 4 s after the cessation of g-ray activity. We fit a power-law function to the data using ...the revised trigger time given by Chincarini and coworkers, and a smoothly broken power-law to the data using the original trigger disseminated through the GCN notices. Including the RAPTOR data from Wo zniak and coworkers, the best-fit power-law indices are a = -0.854 c 0.014 for the single power-law and a sub(1) = -0.364 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(2) sub(1) super(0) sub(9), a sub(2) = -0.881 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(3) sub(3) super(0) sub(1), with a break at t sub(b) = 418 super(+) sub(-) super(3) sub(3) super(1) sub(0) s for the smoothly broken fit. We discuss the fit results, with emphasis placed on the importance of knowing the true start time of the optical transient for this multipeaked burst. As Swift continues to provide prompt GRB locations, it becomes more important to answer the question, "when does the afterglow begin?" in order to correctly interpret the light curves.
We present VLT FORS1 and FORS2 spectra of 39 candidate high-redshift supernovae that were discovered as part of a cosmological study using type Ia supernovae (SNe Ia) over a wide range of redshifts. ...From the spectra alone, 20 candidates are spectrally classified as SNe Ia with redshifts ranging from z = 0.212 to z = 1.181. Of the remaining 19 candidates, 1 might be a type II supernova and 11 exhibit broad supernova-like spectral features and/or have supernova-like light curves. The candidates were discovered in 8 separate ground-based searches. In those searches in which SNe Ia at z similar to 0.5 were targeted, over 80% of the observed candidates were spectrally classified as SNe Ia. In those searches in which SNe Ia with z > 1 were targeted, 4 candidates with z > 1 were spectrally classified as SNe Ia and later followed with ground and space based observatories. We present the spectra of all candidates, including those that could not be spectrally classified as supernova.
A
bstract
This paper describes a measurement of light-by-light scattering based on Pb+Pb collision data recorded by the ATLAS experiment during Run 2 of the LHC. The study uses 2
.
2 nb
−
1
of ...integrated luminosity collected in 2015 and 2018 at
s
NN
= 5
.
02 TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy
E
T
γ
>
2
.
5 GeV, pseudorapidity
|η
γ
| <
2
.
37, diphoton invariant mass
m
γγ
>
5 GeV, and with small diphoton transverse momentum and diphoton acoplanarity. The integrated and differential fiducial cross sections are measured and compared with theoretical predictions. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles. This result provides the most stringent limits to date on axion-like particle production for masses in the range 6–100 GeV. Cross sections above 2 to 70 nb are excluded at the 95% CL in that mass interval.
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