5,212 research outputs found
Bistable Gestalts reduce activity in the whole of V1, not just the retinotopically predicted parts
Activity in the primary visual cortex reduces when certain stimuli can be perceptually organized as a unified Gestalt. This reduction could offer important insights into the nature of feedback computations within the human visual system; however, the properties of this response reduction have not yet been investigated in detail. Here we replicate this reduced V1 response, but find that the modulation in V1 (and V2) to the perceived organization of the input is not specific to the retinotopic location at which the sensory input from that stimulus is represented. Instead, we find a response modulation that is equally evident across the primary visual cortex. Thus in contradiction to some models of hierarchical predictive coding, the perception of an organized Gestalt causes a broad feedback effect that does not act specifically on the part of the retinotopic map representing the sensory input
Kaluza-Klein supergravity on AdS_3 x S^3
We construct a Chern-Simons type gauged N=8 supergravity in three spacetime
dimensions with gauge group SO(4) x T_\infty over the infinite dimensional
coset space SO(8,\infty)/(SO(8) x SO(\infty)), where T_\infty is an infinite
dimensional translation subgroup of SO(8,\infty). This theory describes the
effective interactions of the (infinitely many) supermultiplets contained in
the two spin-1 Kaluza-Klein towers arising in the compactification of N=(2,0)
supergravity in six dimensions on AdS_3 x S^3 with the massless supergravity
multiplet. After the elimination of the gauge fields associated with T_\infty,
one is left with a Yang Mills type gauged supergravity with gauge group SO(4),
and in the vacuum the symmetry is broken to the (super-)isometry group of AdS_3
x S^3, with infinitely many fields acquiring masses by a variant of the
Brout-Englert-Higgs effect.Comment: LaTeX2e, 24 pages; v2: references update
Supergravity, Supermembrane and M(atrix) model on PP-Waves
In the first part of this paper, we study the back-reaction of large-N light
cone momentum on the maximally supersymmetric anti-pp-wave background. This
gives the type IIA geometry of large-N D0-branes on curved space with fluxes.
By taking an appropriate decoupling limit, we conjecture a new duality between
string theory on that background and dual field theory on D0-branes which we
derive by calculating linear coupling terms. Agreement of decoupling
quantities, SO(3) \times SO(6) isometry and Higgs branch on both theories are
shown. Also we find whenever dual field theory is weakly coupled, the curvature
of the geometry is large. In the second part of this paper, we derive the
supermembrane action on a general pp-wave background only through the
properties of null Killing vector and through this, derive the Matrix model.Comment: 19 pages, LaTeX. v2: corrected interpretation of supergravity
solutio
Randomized phase III KEYNOTE-045 trial of pembrolizumab versus paclitaxel, docetaxel, or vinflunine in recurrent advanced urothelial cancer: results of >2 years of follow-up.
BackgroundNovel second-line treatments are needed for patients with advanced urothelial cancer (UC). Interim analysis of the phase III KEYNOTE-045 study showed a superior overall survival (OS) benefit of pembrolizumab, a programmed death 1 inhibitor, versus chemotherapy in patients with advanced UC that progressed on platinum-based chemotherapy. Here we report the long-term safety and efficacy outcomes of KEYNOTE-045.Patients and methodsAdult patients with histologically/cytologically confirmed UC whose disease progressed after first-line, platinum-containing chemotherapy were enrolled. Patients were randomly assigned 1 : 1 to receive pembrolizumab [200 mg every 3 weeks (Q3W)] or investigator's choice of paclitaxel (175 mg/m2 Q3W), docetaxel (75 mg/m2 Q3W), or vinflunine (320 mg/m2 Q3W). Primary end points were OS and progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) by blinded independent central radiology review (BICR). A key secondary end point was objective response rate per RECIST v1.1 by BICR.ResultsA total of 542 patients were enrolled (pembrolizumab, n = 270; chemotherapy, n = 272). Median follow-up as of 26 October 2017 was 27.7 months. Median 1- and 2-year OS rates were higher with pembrolizumab (44.2% and 26.9%, respectively) than chemotherapy (29.8% and 14.3%, respectively). PFS rates did not differ between treatment arms; however, 1- and 2-year PFS rates were higher with pembrolizumab. The objective response rate was also higher with pembrolizumab (21.1% versus 11.0%). Median duration of response to pembrolizumab was not reached (range 1.6+ to 30.0+ months) versus chemotherapy (4.4 months; range 1.4+ to 29.9+ months). Pembrolizumab had lower rates of any grade (62.0% versus 90.6%) and grade ≥3 (16.5% versus 50.2%) treatment-related adverse events than chemotherapy.ConclusionsLong-term results (>2 years' follow-up) were consistent with those of previously reported analyses, demonstrating continued clinical benefit of pembrolizumab over chemotherapy for efficacy and safety for treatment of locally advanced/metastatic, platinum-refractory UC.Trial registrationClinicalTrials.gov: NCT02256436
2021 occultations and transits of Linus orbiting (22) Kalliope: I. Polygonal and `cliptracing' algorithm
The satellite Linus orbiting the main-belt asteroid (22) Kalliope exhibited
occultation and transit events in late 2021. A photometric campaign was
organized and observations were taken by the TRAPPIST-South, SPECULOOS-Artemis,
OWL-Net, and BOAO telescopes, with the goal to constrain models of this system.
Our dynamical model is complex, with multipoles (up to the order ),
internal tides, and external tides. The model was constrained by astrometry
(spanning 2001--2021), occultations, adaptive-optics imaging, calibrated
photometry, as well as relative photometry. Our photometric model was
substantially improved. A new precise () light curve
algorithm was implemented, based on polygon intersections, which are computed
exactly -- by including partial eclipses and partial visibility of polygons.
Moreover, we implemented a `cliptracing' algorithm, based again on polygon
intersections, in which partial contributions to individual pixels are computed
exactly. Both synthetic light curves and synthetic images are then very smooth.
Based on our combined solution, we confirmed the size of Linus, . However, this solution exhibits some tension between the light
curves and the PISCO speckle-interferometry dataset. In most solutions, Linus
is darker than Kalliope, with the albedos vs. . This
is confirmed on deconvolved images. A~detailed revision of astrometric data
allowed us to revise also the value of Kalliope. Most
importantly, a~homogeneous body is excluded. For a differentiated body, two
solutions exist: low-oblateness (), with a~spherical iron
core, and alternatively, high-oblateness () with an
elongated iron core. These correspond to the low- and high-energy collisions,
respectively, studied by means of SPH simulations in our previous work.Comment: Astronomy and Astrophysics, accepte
Chern-Simons Vortices in Supergravity
We study supersymmetric vortex solutions in three-dimensional abelian gauged
supergravity. First, we construct the general U(1)-gauged D=3, N=2 supergravity
whose scalar sector is an arbitrary Kahler manifold with U(1) isometry. This
construction clarifies the connection between local supersymmetry and the
specific forms of some scalar potentials previously found in the literature --
in particular, it provides the locally supersymmetric embedding of the abelian
Chern-Simons Higgs model. We show that the Killing spinor equations admit
rotationally symmetric vortex solutions with asymptotically conical geometry
which preserve half of the supersymmetry.Comment: 26 pages, LaTeX2
M-theory on a Time-dependent Plane-wave
We propose a matrix model on a homogeneous plane-wave background with 20
supersymmetries. This background is anti-Mach type and is equivalent to the
time-dependent background. We study supersymmetries in this theory and
calculate the superalgebra. The vacuum energy of the abelian part is also
calculated. In addition we find classical solutions such as graviton solution,
fuzzy sphere and hyperboloid.Comment: 19pages, no figures, LaTeX, JHEP3.cl
The Intermediate Coupling Regime in the AdS/CFT Correspondence
The correspondence between the 't Hooft limit of N=4 super Yang-Mills theory
and tree-level IIB superstring theory on AdS(5)xS(5) in a Ramond-Ramond
background at values of lambda=g^2 N ranging from infinity to zero is examined
in the context of unitarity. A squaring relation for the imaginary part of the
holographic scattering of identical string fields in the two-particle channels
is found, and a mismatch between weak and strong 't Hooft coupling is pointed
out within the correspondence. Several interpretations and implications are
proposed.Comment: 10 pages, LaTeX, reference adde
Model of M-theory with Eleven Matrices
We show that an action of a supermembrane in an eleven-dimensional spacetime
with a semi-light-cone gauge can be written only with Nambu-Poisson bracket and
an invariant symmetric bilinear form under an approximation. Thus, the action
under the conditions is manifestly covariant under volume preserving
diffeomorphism even when the world-volume metric is flat. Next, we propose two
3-algebraic models of M-theory which are obtained as a second quantization of
an action that is equivalent to the supermembrane action under the
approximation. The second quantization is defined by replacing Nambu-Poisson
bracket with finite-dimensional 3-algebras' brackets. Our models include eleven
matrices corresponding to all the eleven space-time coordinates in M-theory
although they possess not SO(1,10) but SO(1,2) x SO(8) or SO(1,2) x SU(4) x
U(1) covariance. They possess N=1 space-time supersymmetry in eleven dimensions
that consists of 16 kinematical and 16 dynamical ones. We also show that the
SU(4) model with a certain algebra reduces to BFSS matrix theory if DLCQ limit
is taken.Comment: 20 pages, references, a table and discussions added, typos correcte
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