Simple and Sensitive HPLC Method with Fluorescence Detection for the Measurement of Ibuprofen in Rat Plasma: Application to a Long-Lasting Dosage Form

A simple and sensitive high-performance liquid chromatography (HPLC) assay applied to the measurement of ibuprofen in rat plasma has been developed. Two parameters have been investigated to improve ibuprofen detectability using fluorescence detection: variation of mobile phase pH and the use of β-cyclodextrin (β-CD). Increasing the pH value from 2.5 to 6.5 and adding 5 mM β-CD enhanced the fluorescence signal (λ_exc = 224 nm; λ_em = 290 nm) by 2.5 and 1.3-fold, respectively, when using standards. In the case of plasma samples, only pH variation significantly lowered detection and quantification limits, down to 10 and 35 ng/mL, respectively. Full selectivity was obtained with a single step for plasma treatment, that is, protein precipitation with acidified acetonitrile. The validated method was applied to a pharmacokinetic study of ibuprofen encapsulated in microspheres and subcutaneously administered to rats.     

Dodecylhydroxydiphosphonic Acid for Solvent Extraction

Abstract

The extraction behavior of Zn(II) and Cu(II) in acetate media has been investigated using dodecylhydroxydiphosphonic acid, DHDPA, which was previously synthesized and characterized. The extraction of both cations was carried out in different media with the addition of CH₃COOH, HCl or H₂SO₄ at different pH. The maximum extraction yield of 80% for zinc, was obtained in one step after the addition of sulfuric acid at pH_i=5.5 and for copper after the addition of 10 mg of sodium acetate. The authors plan additional tests using polar solvents.     

Stabilized active camera tracking system

We present a robust and real-time stabilized active camera tracking system (ACTS), which consists of three algorithmic modules: visual tracking, pan-tilt control, and digital video stabilization. We propose an efficient correlation-based framework for visual tracking module that is designed to handle the problems which severely deteriorate the performance of a traditional tracker. The problems that it handles are template drift, noise, object fading (obscuration), background clutter, intermittent occlusion, varying illumination in the scene, high computational complexity, and varying shape, scale, and velocity of the manoeuvring object during its motion. The pan-tilt control module is a predictive open-loop car-following control strategy, which moves the camera efficiently and smoothly so that the target being tracked is always at the center of the video frame. Video stabilization module is required to eliminate the vibration in the video, when the system is mounted on a vibratory platform such as truck, helicopter, ship, etc. We present a very efficient video stabilization method that adds no extra computational overhead to the overall system. It exploits the coordinates of the target, computed by the tracker module, to sense the amount of vibration and then filters it out of the video. The proposed system works at full frame rate (30 fps), and has been successfully used in uncontrolled real-world environment. Experimental results show the efficiency, precision, and robustness of the proposed stabilized ACTS.     

Evolutionary research of optimal strategies for exclusive positioned clustering in simulated environment of collective robotics

One of the captivating characteristics of social insects, in spite of their rudimentary individual constitution, is the ability by which they have to solve complicated problems in an elastic and robust way. This includes elasticity which ensures the adaptation of the insect system to the unpredictable changes of their environment, and robustness which guarantees a functioning continuity of the system, in spite of the possible failure of a certain number of its elements in the achievement of their individual missions. From this point of view, fields of research have emerged over the past decades, with the aim of trying to reveal the secret behind the relationship between individual and society, so perfectly designed in nature. Collective robotics is one of those fields where we try to find microscopic rules allowing a group of autonomous robots, mobile and with limited capacity, to carry out a specific macro-task, such as exclusive positioned heap formation. The idea, behind this, is to use a model of oriented reactive agent simulation, to seek the relations which can link the local perceptions of the simulated robots with their basic actions, in order to make the above mentioned gathering task a success. An evolutionary approach is used for this purpose, making it possible to discover the functional control relations of these simulated robots. An analogy with the precepts specific to the ant community is established and results of simulation indicating the effectiveness of the detected rules are presented.     

Recovery from multiple simultaneous failures in wireless sensor networks using minimum Steiner tree

In some applications, wireless sensor networks (WSNs) operate in very harsh environments and nodes become subject to increased risk of damage. Sometimes a WSN suffers from the simultaneous failure of multiple sensors and gets partitioned into disjoint segments. Restoring network connectivity in such a case is crucial in order to avoid negative effects on the application. Given that WSNs often operate unattended in remote areas, the recovery should be autonomous. This paper promotes an effective strategy for restoring the connectivity among these segments by populating the least number of relay nodes. Finding the optimal count and position of relay nodes is NP-hard and heuristics are thus pursued. We propose a Distributed algorithm for Optimized Relay node placement using Minimum Steiner tree (DORMS). Since in autonomously operating WSNs it is infeasible to perform a network-wide analysis to diagnose where segments are located, DORMS moves relay nodes from each segment toward the center of the deployment area. As soon as those relays become in range of each other, the partitioned segments resume operation. DORMS further model such initial inter-segment topology as Steiner tree in order to minimize the count of required relays. Disengaged relays can return to their respective segments to resume their pre-failure duties. We analyze DORMS mathematically and explain the beneficial aspects of the resulting topology with respect to connectivity, and traffic balance. The performance of DORMS is validated through extensive simulation experiments.     

An efficient heuristic for reliability design optimization problems

This paper develops an efficient heuristic to solve two typical combinatorial optimization problems frequently met when designing highly reliable systems. The first one is the redundancy allocation problem (RAP) of series-parallel binary-state systems. The design goal of the RAP is to select the optimal combination of elements and redundancy levels to maximize system reliability subject to the system budget and to the system weight. The second problem is the expansion-scheduling problem (ESP) of multi-state series-parallel systems. In this problem, the study period is divided into several stages. At each stage, the demand is represented as a piecewise cumulative load curve. During the system lifetime, the demand can increase and the total productivity may become insufficient to assume the demand. To increase the total system productivity, elements are added to the existing system. The objective in the ESP is to minimize the sum of costs of the investments over the study period while satisfying availability constraints at each stage. The heuristic approach developed to solve the RAP and the ESP is based on a combination of space partitioning, genetic algorithms (GA) and tabu search (TS). After dividing the search space into a set of disjoint subsets, this approach uses GA to select the subspaces, and applies TS to each selected subspace. Numerical results for the test problems from previous research are reported and compared. The results show the advantages of the proposed approach for solving both problems.     

Supplementary Microstructural Features Induced During Laser Surface Melting of Thermally Sprayed Inconel 625 Coatings

Laser surface melting of thermally sprayed coatings has the potential to enhance their corrosion properties by incorporating favorable microstructural changes. Besides homogenizing the as-sprayed structure, laser melting may induce certain microstructural modifications (i.e., supplementary features) in addition to those that directly improve the corrosion performance. Such features, being a direct result of the laser treatment process, are described in this paper which is part of a broader study in which high velocity oxy-fuel sprayed Inconel 625 coatings on mild-steel substrates were treated with a diode laser and the modified microstructure characterized using optical and scanning electron microscopy and x-ray diffraction. The laser treated coating features several different zones, including a region with a microstructure in which there is a continuous columnar dendritic structure through a network of retained oxide stringers.     

Physicochemical Study of Glycerol Hydrogenolysis Over a Ni–Cu/Al2O3 Catalyst Using Formic Acid as the Hydrogen Source

Glycerol hydrogenolysis to propanediols requires the use of hydrogen as reactant. One interesting option is to directly generate this hydrogen in active sites of the support using hydrogen donors, such as formic acid. The effect that the reacting pressure has on glycerol conversion and product selectivity over a Ni–Cu/Al₂O₃ catalyst was studied. The negative effect of decreasing the pressure was much more significant when the source of hydrogen was dissolved molecular hydrogen than when it was formic acid. X-ray photoelectron spectroscopy and temperature programmed reduction measurements were performed to understand the effect of Ni–Cu/Al₂O₃ reduction procedure on the catalytic activity. Semi-batch reactor studies with the Ni–Cu/Al₂O₃ catalyst were carried out with continuous addition of the hydrogen donor to obtain kinetic data. Langmuir–Hinshelwood type models were developed to describe the direct conversion of glycerol into propanediol, and propanediol further hydrogenolysis to 1-propanol. The model included the competitive adsorption between both glycols. These models were used to obtain valuable data for the optimization of the process.     

Convergence of a general iterative scheme for a finite family of asymptotically quasi-nonexpansive mappings in convex metric spaces and applications

In this paper, we introduce the iterative scheme due to Khan, Domlo and Fukhar-ud-din (2008) [8] in convex metric spaces and establish strong convergence of this scheme to a unique common fixed point of a finite family of asymptotically quasi-nonexpansive mappings. As a consequence of our result, we obtain some related convergence theorems. Our results generalize some recent results obtained in [8].