Direct evidence for the Maldacena conjecture for N=(8,8) super Yang-Mills theory in 1+1 dimensions

We solve N=(8,8) super Yang-Mills theory in 1+1 dimensions at strong coupling to directly confirm the predictions of supergravity at weak coupling. We do our calculations in the large-N_c approximation using Supersymmetric Discrete Light-Cone Quantization with up to 3*10^{12} basis states. We calculate the stress-energy correlator as a function of the separation r and find that at intermediate values of r the correlator behaves as r^{-5} to within errors as predicted by weak-coupling supergravity. We also present an extension to significantly higher resolution of our earlier results for the same correlator in the N=(2,2) theory and see that in this theory the correlator has very different behavior at intermediate values of r.Comment: 12 pp., 6 figures, LaTe

Two-boson truncation of Pauli-Villars-regulated Yukawa theory

We apply light-front quantization, Pauli-Villars regularization, and numerical techniques to the nonperturbative solution of the dressed-fermion problem in Yukawa theory in 3+1 dimensions. The solution is developed as a Fock-state expansion truncated to include at most one fermion and two bosons. The basis includes a negative-metric heavy boson and a negative-metric heavy fermion in order to provide the necessary cancellations of ultraviolet divergences. The integral equations for the Fock-state wave functions are solved by reducing them to effective one-boson--one-fermion equations for eigenstates with J_z=1/2. The equations are converted to a matrix equation with a specially tuned quadrature scheme, and the lowest mass state is obtained by diagonalization. Various properties of the dressed-fermion state are then computed from the nonperturbative light-front wave functions. This work is a major step in our development of Pauli-Villars regularization for the nonperturbative solution of four-dimensional field theories and represents a significant advance in the numerical accuracy of such solutions.Comment: 32 pages, 17 figures; requires elsart.cl

Aspirin inhibits the acute venodilator response to furosemide in patients with chronic heart failure

OBJECTIVES: We sought to determine the effect of aspirin on the venodilator effect of furosemide in patients with chronic heart failure (CHF) BACKGROUND: Furosemide has an acute venodilator effect preceding its diuretic action, which is blocked by nonsteroidal anti-inflammatory drugs. The ability of therapeutic doses of aspirin to block this effect of furosemide in patients with CHF has not been studied. For comparison, the venodilator response to nitroglycerin (NTG) was also studied. METHODS: Eleven patients with CHF were randomized to receive placebo, aspirin at 75 mg/day or aspirin at 300 mg/day for 14 days in a double-blind, crossover study. The effect of these pretreatments on the change in forearm venous capacitance (FVC) after 20 mg of intravenous furosemide was measured over 20 min by using venous occlusion plethysmography. In a second study, the effect of 400 μg of sublingual NTG on FVC was documented in 11 similar patients (nine participated in the first study). RESULTS: Mean arterial pressure, heart rate and forearm blood flow did not change in response to furosemide. After placebo pretreatment, furosemide caused an increase in FVC of 2.2% (95% confidence interval [CI] −0.9% to 5.2%; mean response over 20 min). By comparison, FVC fell by −1.1% (95% CI −4.2% to 1.9%) after pretreatment with aspirin at 75 mg/day, and by −3.7% (95% CI −6.8% to −0.7%) after aspirin at 300 mg/day (p = 0.020). In the second study, NTG increased FVC by 2.1% (95% CI −1.6% to 5.8%) (p = 0.95 vs. furosemide). CONCLUSIONS: In patients with CHF, venodilation occurs within minutes of the administration of intravenous dose of furosemide. Our observation that aspirin inhibits this effect further questions the use of aspirin in patients with CHF

3D tumor localization through real-time volumetric x-ray imaging for lung cancer radiotherapy

Recently we have developed an algorithm for reconstructing volumetric images and extracting 3D tumor motion information from a single x-ray projection. We have demonstrated its feasibility using a digital respiratory phantom with regular breathing patterns. In this work, we present a detailed description and a comprehensive evaluation of the improved algorithm. The algorithm was improved by incorporating respiratory motion prediction. The accuracy and efficiency were then evaluated on 1) a digital respiratory phantom, 2) a physical respiratory phantom, and 3) five lung cancer patients. These evaluation cases include both regular and irregular breathing patterns that are different from the training dataset. For the digital respiratory phantom with regular and irregular breathing, the average 3D tumor localization error is less than 1 mm. On an NVIDIA Tesla C1060 GPU card, the average computation time for 3D tumor localization from each projection ranges between 0.19 and 0.26 seconds, for both regular and irregular breathing, which is about a 10% improvement over previously reported results. For the physical respiratory phantom, an average tumor localization error below 1 mm was achieved with an average computation time of 0.13 and 0.16 seconds on the same GPU card, for regular and irregular breathing, respectively. For the five lung cancer patients, the average tumor localization error is below 2 mm in both the axial and tangential directions. The average computation time on the same GPU card ranges between 0.26 and 0.34 seconds

Spatial re-organization of myogenic regulatory sequences temporally controls gene expression

During skeletal muscle differentiation, the activation of some tissue-specific genes occurs immediately while others are delayed. The molecular basis controlling temporal gene regulation is poorly understood. We show that the regulatory sequences, but not other regions of genes expressed at late times of myogenesis, are in close physical proximity in differentiating embryonic tissue and in differentiating culture cells, despite these genes being located on different chromosomes. Formation of these inter-chromosomal interactions requires the lineage-determinant MyoD and functional Brg1, the ATPase subunit of SWI/SNF chromatin remodeling enzymes. Ectopic expression of myogenin and a specific Mef2 isoform induced myogenic differentiation without activating endogenous MyoD expression. Under these conditions, the regulatory sequences of late gene loci were not in close proximity, and these genes were prematurely activated. The data indicate that the spatial organization of late genes contributes to temporal regulation of myogenic transcription by restricting late gene expression during the early stages of myogenesis. The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research

On the nonperturbative solution of Pauli--Villars-regulated light-front QED: A comparison of the sector-dependent and standard parameterizations

We consider quantum electrodynamics quantized on the light front in Feynman gauge and regulated in the ultraviolet by the inclusion of massive, negative-metric Pauli--Villars (PV) particles in the Lagrangian. The eigenstate of the electron is approximated by a Fock-state expansion truncated to include one photon. The Fock-state wave functions are computed from the fundamental Hamiltonian eigenvalue problem and used to calculate the anomalous magnetic moment, as a point of comparison. Two approaches are considered: a sector-dependent parameterization, where the bare parameters of the Lagrangian are allowed to depend on the Fock sectors between which the particular Hamiltonian term acts, and the standard choice, where the bare parameters are the same for all sectors. Both methods are shown to require some care with respect to ultraviolet divergences; neither method can allow all PV masses to be taken to infinity. In addition, the sector-dependent approach suffers from an infrared divergence that requires a nonzero photon mass; due to complications associated with this divergence, the standard parameterization is to be preferred. We also show that the self-energy effects obtained from a two-photon truncation are enough to bring the standard-parameterization result for the anomalous moment into agreement with experiment within numerical errors. This continues the development of a method for the nonperturbative solution of strongly coupled theories, in particular quantum chromodynamics.Comment: 28 pages, 2 figures, LaTeX with elsarticle.cl