17 research outputs found
Measuring eccentricity in binary black-hole initial data
Initial data for evolving black-hole binaries can be constructed via many
techniques, and can represent a wide range of physical scenarios. However,
because of the way that different schemes parameterize the physical aspects of
a configuration, it is not alway clear what a given set of initial data
actually represents. This is especially important for quasiequilibrium data
constructed using the conformal thin-sandwich approach. Most initial-data
studies have focused on identifying data sets that represent binaries in
quasi-circular orbits. In this paper, we consider initial-data sets
representing equal-mass black holes binaries in eccentric orbits. We will show
that effective-potential techniques can be used to calibrate initial data for
black-hole binaries in eccentric orbits. We will also examine several different
approaches, including post-Newtonian diagnostics, for measuring the
eccentricity of an orbit. Finally, we propose the use of the ``Komar-mass
difference'' as a useful, invariant means of parameterizing the eccentricity of
relativistic orbits.Comment: 12 pages, 11 figures, submitted to Physical Review D, revtex
Circular orbits and spin in black-hole initial data
The construction of initial data for black-hole binaries usually involves the
choice of free parameters that define the spins of the black holes and
essentially the eccentricity of the orbit. Such parameters must be chosen
carefully to yield initial data with the desired physical properties. In this
paper, we examine these choices in detail for the quasiequilibrium method
coupled to apparent-horizon/quasiequilibrium boundary conditions. First, we
compare two independent criteria for choosing the orbital frequency, the
"Komar-mass condition" and the "effective-potential method," and find excellent
agreement. Second, we implement quasi-local measures of the spin of the
individual holes, calibrate these with corotating binaries, and revisit the
construction of non-spinning black hole binaries. Higher-order effects, beyond
those considered in earlier work, turn out to be important. Without those,
supposedly non-spinning black holes have appreciable quasi-local spin;
furthermore, the Komar-mass condition and effective potential method agree only
when these higher-order effects are taken into account. We compute a new
sequence of quasi-circular orbits for non-spinning black-hole binaries, and
determine the innermost stable circular orbit of this sequence.Comment: 24 pages, 17 figures, accepted for publication in Physical Review D,
revtex4; Fixed error in computing proper separation and updated figures and
tables accordingly, added reference to Sec. IV.A, fixed minor error in Sec.
IV.B, added new data to Tables IV and V, fixed 1 reference, fixed error in
Eq. (A7b), included minor changes from PRD editin
Error-analysis and comparison to analytical models of numerical waveforms produced by the NRAR Collaboration
The Numerical-Relativity-Analytical-Relativity (NRAR) collaboration is a
joint effort between members of the numerical relativity, analytical relativity
and gravitational-wave data analysis communities. The goal of the NRAR
collaboration is to produce numerical-relativity simulations of compact
binaries and use them to develop accurate analytical templates for the
LIGO/Virgo Collaboration to use in detecting gravitational-wave signals and
extracting astrophysical information from them. We describe the results of the
first stage of the NRAR project, which focused on producing an initial set of
numerical waveforms from binary black holes with moderate mass ratios and
spins, as well as one non-spinning binary configuration which has a mass ratio
of 10. All of the numerical waveforms are analysed in a uniform and consistent
manner, with numerical errors evaluated using an analysis code created by
members of the NRAR collaboration. We compare previously-calibrated,
non-precessing analytical waveforms, notably the effective-one-body (EOB) and
phenomenological template families, to the newly-produced numerical waveforms.
We find that when the binary's total mass is ~100-200 solar masses, current EOB
and phenomenological models of spinning, non-precessing binary waveforms have
overlaps above 99% (for advanced LIGO) with all of the non-precessing-binary
numerical waveforms with mass ratios <= 4, when maximizing over binary
parameters. This implies that the loss of event rate due to modelling error is
below 3%. Moreover, the non-spinning EOB waveforms previously calibrated to
five non-spinning waveforms with mass ratio smaller than 6 have overlaps above
99.7% with the numerical waveform with a mass ratio of 10, without even
maximizing on the binary parameters.Comment: 51 pages, 10 figures; published versio
31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two
Background
The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd.
Methods
We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background.
Results
First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001).
Conclusions
In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival
Fall, recovery, and characterization of the Novato L6 chondrite breccia
The Novato L6 chondrite fragmental breccia fell in California on 17 October 2012, and was recovered after the Cameras for Allsky Meteor Surveillance (CAMS) project determined the meteor's trajectory between 95 and 46 km altitude. The final fragmentation from 42 to 22 km altitude was exceptionally well documented by digital photographs. The first sample was recovered before rain hit the area. First results from a consortium study of the meteorite's characterization, cosmogenic and radiogenic nuclides, origin, and conditions of the fall are presented. Some meteorites did not retain fusion crust and show evidence of spallation. Before entry, the meteoroid was 35 +/- 5 cm in diameter (mass 80 +/- 35 kg) with a cosmic-ray exposure age of 9 +/- 1 Ma, if it had a one-stage exposure history. A two-stage exposure history is more likely, with lower shielding in the last few Ma. Thermoluminescence data suggest a collision event within the last similar to 0.1 Ma. Novato probably belonged to the class of shocked L chondrites that have a common shock age of 470 Ma, based on the U, Th-He age of 420 +/- 220 Ma. The measured orbits of Novato, Jesenice, and Innisfree are consistent with a proposed origin of these shocked L chondrites in the Gefion asteroid family, perhaps directly via the 5: 2 mean-motion resonance with Jupiter. Novato experienced a stronger compaction than did other L6 chondrites of shock-stage S4. Despite this, a freshly broken surface shows a wide range of organic compounds