Inversion formulas for the broken-ray Radon transform

We consider the inverse problem of the broken ray transform (sometimes also referred to as the V-line transform). Explicit image reconstruction formulas are derived and tested numerically. The obtained formulas are generalizations of the filtered backprojection formula of the conventional Radon transform. The advantages of the broken ray transform include the possibility to reconstruct the absorption and the scattering coefficients of the medium simultaneously and the possibility to utilize scattered radiation which, in the case of the conventional X-ray tomography, is typically discarded.Comment: To be submitted to Inverse Problem

XML Reconstruction View Selection in XML Databases: Complexity Analysis and Approximation Scheme

Query evaluation in an XML database requires reconstructing XML subtrees rooted at nodes found by an XML query. Since XML subtree reconstruction can be expensive, one approach to improve query response time is to use reconstruction views - materialized XML subtrees of an XML document, whose nodes are frequently accessed by XML queries. For this approach to be efficient, the principal requirement is a framework for view selection. In this work, we are the first to formalize and study the problem of XML reconstruction view selection. The input is a tree $T$, in which every node $i$ has a size $c_i$ and profit $p_i$, and the size limitation $C$. The target is to find a subset of subtrees rooted at nodes $i_1,\cdots, i_k$ respectively such that $c_{i_1}+\cdots +c_{i_k}\le C$, and $p_{i_1}+\cdots +p_{i_k}$ is maximal. Furthermore, there is no overlap between any two subtrees selected in the solution. We prove that this problem is NP-hard and present a fully polynomial-time approximation scheme (FPTAS) as a solution

Description of non-specific DNA-protein interaction and facilitated diffusion with a dynamical model

We propose a dynamical model for non-specific DNA-protein interaction, which is based on the 'bead-spring' model previously developed by other groups, and investigate its properties using Brownian Dynamics simulations. We show that the model successfully reproduces some of the observed properties of real systems and predictions of kinetic models. For example, sampling of the DNA sequence by the protein proceeds via a succession of 3d motion in the solvent, 1d sliding along the sequence, short hops between neighboring sites, and intersegmental transfers. Moreover, facilitated diffusion takes place in a certain range of values of the protein effective charge, that is, the combination of 1d sliding and 3d motion leads to faster DNA sampling than pure 3d motion. At last, the number of base pairs visited during a sliding event is comparable to the values deduced from single-molecule experiments. We also point out and discuss some discrepancies between the predictions of this model and some recent experimental results as well as some hypotheses and predictions of kinetic models

Microscopic derivation of the Jaynes-Cummings model with cavity losses

In this paper we provide a microscopic derivation of the master equation for the Jaynes-Cummings model with cavity losses. We single out both the differences with the phenomenological master equation used in the literature and the approximations under which the phenomenological model correctly describes the dynamics of the atom-cavity system. Some examples wherein the phenomenological and the microscopic master equations give rise to different predictions are discussed in detail.Comment: 9 pages, 3 figures New version with minor correction Accepted for publication on Physical Review

Switchable lasing in coupled multimode microcavities

We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by re-seeding the cavity after a short cool-down period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented.Comment: Accepted for publication in Physical Review Letters. Published, somewhat shortened versio

A Randomized Parallel Controlled Study of the Efficacy and Safety of Lornoxicam Versus Etoricoxib after Total Knee Arthroplasty

Objectives: The aim of the study was to compare the postoperative analgesic efficacy and safety of lornoxicam versus etoricoxib for the first 48 hours after surgery. Methods: We conducted a prospective randomized controlled study on 110 patients ASAI-II scheduled for TKA under spinal anesthesia, who received either lornoxicam 8 mg PO at the end of surgery and a further 8 mg after 12 hours (Lornoxicam Group) or etoricoxib 120 mg at the end of surgery and one placebo pill after 12 hours (Etoricoxib Group). The primary outcome measure was the cumulative dose of morphine administered during the first postoperative 24 and 48 hours. Secondary outcomes were duration of analgesia and the side effects of the treatment. Results: The groups were similar in terms of demographic data. There are no significant differences between groups regarding the morphine consumption at 24 hours (36.2 ± 12 in Lornoxicam group and 34.5 ± 14.1 in Etoricoxib group) and 48 hours postoperatively (15.6 ± 12.8 in Lornoxicam group and 18 ± 12.3 in Etoricoxib group) or between the duration of analgesia (314.5 ± 70.4 in Lornoxicam group and 320.4 ± 89.2 in Etoricoxib group). Conclusion: Postoperative use of lornoxicam for 48 hours in the dose of 8 mg PO twice a day in patients undergoing TKA has an analgetic effect comparable to etoricoxib 120 mg, fewer patients experienced adverse symptoms in the etoricoxib group, but the difference was not statistically significant

Qualitative aspects of the entanglement in the three-level model with photonic crystals

This communication is an enquiry into the circumstances under which concurrence and phase entropy methods can give an answer to the question of quantum entanglement in the composite state when the photonic band gap is exhibited by the presence of photonic crystals in a three-level system. An analytic approach is proposed for any three-level system in the presence of photonic band gap. Using this analytic solution, we conclusively calculate the concurrence and phase entropy, focusing particularly on the entanglement phenomena. Specifically, we use concurrence as a measure of entanglement for dipole emitters situated in the thin slab region between two semi-infinite one-dimensionally periodic photonic crystals, a situation reminiscent of planar cavity laser structures. One feature of the regime considered here is that closed-form evaluation of the time evolution may be carried out in the presence of the detuning and the photonic band gap, which provides insight into the difference in the nature of the concurrence function for atom-field coupling, mode frequency and different cavity parameters. We demonstrate how fluctuations in the phase and number entropies effected by the presence of the photonic-band-gap. The outcomes are illustrated with numerical simulations applied to GaAs. Finally, we relate the obtained results to instances of any three-level system for which the entanglement cost can be calculated. Potential experimental observations in solid-state systems are discussed and found to be promising.Comment: 28 pages, 10 figures: Accepted in Applied Physics B: Laser and Optic

Cavity Modes Study in Hyperuniform Disordered Photonic Bandgap Materials

We introduce novel architecture for cavity design in an isotropic disordered photonic band gap material. We demonstrate that point-like defects can support localized modes with different symmetries and multiple resonant frequencies, useful for various applications