Esophagitis in Sprague-Dawley rats is mediated by free radicals

Free radical-mediated esophagitis was studied during duodenogastroesophageal reflux (mixed reflux) or acid reflux in rats. The influence of reflux on esophageal glutathione levels was also examined. Mixed reflux caused more gross mucosal injury than acid reflux. Gross mucosal injury occurred in the mid-esophagus. Total glutathione (GSH) in the esophageal mucosa of control rats was highest in the distal esophagus. The time course of esophageal GSH in rats treated by mixed reflux showed a significant decrease 4 hr after initiation of reflux, followed by a significant increase from the 12th hour on. Mucosal GSH was increased in both reflux groups after 24 hr but significantly more so in the mixed than in the acid reflux group. The free radical scavenger superoxide dismutase (SOD) prevented esophagitis and was associated with decreased GSH levels. GSH depletion by buthionine sulfoximine (BSO) prevented esophagitis and stimulated SOD production in the esophageal mucosa. It is concluded that gastroesophageal reflux is associated with oxidative stress in the esophageal mucosa. The lower GSH levels in the mid-esophagus may predispose to damage in this area. Duodenogastroesophageal reflux causes more damage than pure acid reflux. Oxidative stress leads to GSH depletion of the esophageal mucosa in the first few hours following damage but then stimulates GSH production. GSH depletion by BSO does not worsen esophagitis since it increases the esophageal SOD concentration.     

Cdc34 and the F-box protein Met30 are required for degradation of the Cdk-inhibitory kinase Swe1

Ubiquitin-mediated proteolysis controls the abundance of many cell cycle regulatory proteins. Recent work in Saccharomyces cerevisiae suggests that a complex consisting of Cdc53, Skp1, and a third component known as an F-box protein (termed SCF) in combination with Cdc34 specifically targets regulatory proteins for degradation, and that substrate specificity is likely to be mediated by the F-box subunit. A screen for genetic interactions with a cdc34 mutation yielded MET30, which encodes an F-box protein. MET30 is an essential gene required for cell cycle progression and met30 mutations interact genetically with mutations in SCF components. Furthermore, physical interactions between Met30, Cdc53, Cdc34, and Skp1 in vivo provide evidence for an SCFMet30 complex. We demonstrate the involvement of Met30 in the degradation of the Cdk-inhibitory kinase Swe1. Swe1 is stabilized in met30 mutants and GST-Met30 pull-down experiments reveal that Met30 specifically binds Swe1 in vivo. Furthermore, extracts prepared from cdc34 or met30 mutants are defective in polyubiquitination of Swe1. Taken together, these data suggest that SCF-mediated proteolysis may contribute to the regulation of entry into mitosis. Our data, in combination with previously published results, also provide evidence for distinct SCF complexes in vivo and support the idea that their F-box subunits mediate SCF substrate specificity.     

A multiagent approach to managing air traffic flow

Intelligent air traffic flow management is one of the fundamental challenges facing the Federal Aviation Administration (FAA) today. FAA estimates put weather, routing decisions and airport condition induced delays at 1,682,700 h in 2007 (FAA OPSNET Data, US Department of Transportation website, ), resulting in a staggering economic loss of over $41 billion (Joint Economic Commission Majority Staff, Your flight has been delayed again, 2008). New solutions to the flow management are needed to accommodate the threefold increase in air traffic anticipated over the next two decades. Indeed, this is a complex problem where the interactions of changing conditions (e.g., weather), conflicting priorities (e.g., different airlines), limited resources (e.g., air traffic controllers) and heavy volume (e.g., over 40,000 flights over the US airspace) demand an adaptive and robust solution. In this paper we explore a multiagent algorithm where agents use reinforcement learning (RL) to reduce congestion through local actions. Each agent is associated with a fix (a specific location in 2D space) and has one of three actions: setting separation between airplanes, ordering ground delays or performing reroutes. We simulate air traffic using FACET which is an air traffic flow simulator developed at NASA and used extensively by the FAA and industry. Our FACET simulations on both artificial and real historical data from the Chicago and New York airspaces show that agents receiving personalized rewards reduce congestion by up to 80% over agents receiving a global reward and by up to 90% over a current industry approach (Monte Carlo estimation).     

Dispersion in Disks

We present three new approximation algorithms with improved constant ratios for selecting n points in n disks such that the minimum pairwise distance among the points is maximized.

1. A very simple O(nlog?n)-time algorithm with ratio 0.511 for disjoint unit disks.
2. An LP-based algorithm with ratio 0.707 for disjoint disks of arbitrary radii that uses a linear number of variables and constraints, and runs in polynomial time.
3. A hybrid algorithm with ratio either 0.4487 or 0.4674 for (not necessarily disjoint) unit disks that uses an algorithm of Cabello in combination with either the simple O(nlog?n)-time algorithm or the LP-based algorithm.

The LP algorithm can be extended for disjoint balls of arbitrary radii in ? ^d , for any (fixed) dimension d, while preserving the features of the planar algorithm. The algorithm introduces a novel technique which combines linear programming and projections for approximating Euclidean distances. The previous best approximation ratio for dispersion in disjoint disks, even when all disks have the same radius, was 1/2. Our results give a positive answer to an open question raised by Cabello, who asked whether the ratio 1/2 could be improved.     

Design optimization of supersonic jet pumps using high fidelity flow analysis

Supersonic jet pumps are simple devices with no moving parts, where a high velocity (primary) flow is used to pump a second fluid. In this paper, Computational Fluid Dynamics (CFD) is combined with an optimization framework in order to develop a tool for the rapid generation of jet pump designs. A key feature of the problem formulation is the transformation of the jet pump design parameters in terms of geometric ratios. This approach dramatically reduces the number of unrealistic designs covered by the Design of Experiments. Optimal Latin Hypercubes for surrogate model building and model validation points are constructed using a permutation genetic algorithm and design points are evaluated using CFD. Surrogate models of primary and entrained flow rates are built using a Moving Least Squares approach. A series of optimizations for various pump sizes are performed using a genetic algorithm and Sequential Quadratic Programming, with responses calculated from the surrogates. This approach results in a set of optimized designs, from which pumps for a wide range of flow rates can be interpolated.     

Superconductivity,magnetic properties,and specific heat of the pseudoternary,body-centered tetragonal system Ho(Rh1−x Ru x )4B4

The phase boundaries between superconductivity and various types of magnetism in the pseudoternary system Ho(Rh_1–x Ru _x )₄B₄ were examined by low-temperature measurements of the specific heatc(T), dc magnetizationM(H), superconducting upper critical fieldH _c2 (T), and ac susceptibility x_ac (T). For Ru concentrationsx0.37 superconductivity coexists with antiferromagnetic order below about 1 K, as shown by characteristic minima in theH _c2 (T) curves and an extrapolation ofM(H) data. Additionally, theH _c2 (T) measurements exhibit an unusual hysteresis between data taken in increasing and decreasing fields below 0.6 K. As a starting point for a theoretical explanation of this feature, a mean-field model is proposed with antiferromagnetic as well as ferromagnetic interactions, which are tentatively identified as the RKKY and dipole-dipole interactions. The existence of two competing interactions is supported by the observation of a time-dependence of the x_ac signal at 50 mK for 0.40x0.70, leading to a pronounced hysteresis in x_ac (T), which reflects a relaxation of the magnetic structure with time constants of several hours. Forx0.80 the x_ac (T) andM(H) data indicate ferromagnetic ordering withT _m increasing withx. However, an irregular temperature dependence of the Arrott plots forx=1.0 and unusual features of the magneticc(T) anomalies forx=0.95 and 1.0 exclude simple mean-field ferromagnetism. A discussion of the experimental results based on anx-dependent variation of the electronic density of states at the Fermi level is presented.     

Image shifting technique to resolve directional ambiguity in double-pulsed velocity

Image shifting provides a method of determining the direction of displacement, and hence the velocity, for all types of pulsed laser velocimeter. It is independent of the scattering properties of the particles and/or the intensity of the illumination of the first image with respect to the second image, and it is capable of high performance. With rotating mirror systems, image shifting can be used to offset negative velocities up to 10 m/s. With electrooptic systems, it is estimated that image shifting can be used at velocities up to 500 m/s.     

Predictive control architecture for real-time image moments based servoing of robot manipulators

This paper presents a real-time architecture for visual servoing of robot manipulators using nonlinear based predictive control. In order to increase the robustness of the control algorithm, image moments were chosen to be the visual features which describe the objects from the image. A visual predictive architecture is designed to solve tasks addressed to robot manipulators with an eye-in-hand configuration. An implementation of the proposed architecture is done so that the capabilities of a 6 d.o.f robot manipulator are extended. The results of different experiments conducted with two types of image moments based controllers (proportional and predictive with reference trajectory) are presented and discussed.     

Partitioned and Implicit–Explicit General Linear Methods for Ordinary Differential Equations

Implicit–explicit (IMEX) time stepping methods can efficiently solve differential equations with both stiff and nonstiff components. IMEX Runge–Kutta methods and IMEX linear multistep methods have been studied in the literature. In this paper we study new implicit–explicit methods of general linear type. We develop an order conditions theory for high stage order partitioned general linear methods (GLMs) that share the same abscissae, and show that no additional coupling order conditions are needed. Consequently, GLMs offer an excellent framework for the construction of multi-method integration algorithms. Next, we propose a family of IMEX schemes based on diagonally-implicit multi-stage integration methods and construct practical schemes of order up to three. Numerical results confirm the theoretical findings.     

Influence of alginite on the reflectance of vitrinite from Joadja,NSW, and some other coals and oil shales containing alginite

Reflectance data for vitrinite occurring in torbanites indicate that the mean maximum reflectance and the range of reflectance values are significantly lowered by the presence of alginite. This is the probable cause of apparently anomalous rank gradients in some deep oil exploration wells. Intermaceral effects need to be considered in assessing rank or maturity from vitrinite reflectance, and by inference, in most other methods. The interpretation of the cause of the effect is open to further study but the findings are highly significant in relation to coal utilization, oil and gas exploration, and studies of oil shales.