Two-dimensional packing with conflicts

We study the two-dimensional version of the bin packing problem with conflicts. We are given a set of (two-dimensional) squares V = {1, 2, . . . ,n} with sides and a conflict graph G = (V, E). We seek to find a partition of the items into independent sets of G, where each independent set can be packed into a unit square bin, such that no two squares packed together in one bin overlap. The goal is to minimize the number of independent sets in the partition. This problem generalizes the square packing problem (in which we have ) and the graph coloring problem (in which s _i = 0 for all i = 1,2, . . . , sn). It is well known that coloring problems on general graphs are hard to approximate. Following previous work on the one-dimensional problem, we study the problem on specific graph classes, namely, bipartite graphs and perfect graphs. We design a -approximation for bipartite graphs, which is almost best possible (unless P = NP). For perfect graphs, we design a 3.2744-approximation. An extended abstract version of this paper has appeared in Proceedings of the 16th International Symposium on Fundamentals of Computation Theory (FCT 2007), pp 288–299. Rob van Stee was supported by the Alexander von Humboldt Foundation.     

Adsorption of berberine on commercial minerals

There is interest in studying interactions between organic modifiers and raw commercial clays aiming the production of low-cost “organoclays”. In this study we report the interaction between berberine — a monovalent organic cation — and three commercial bentonites and a Turkish zeolite. The Turkish zeolite exhibited adsorption at values of 5–10% of the cation exchange capacity (CEC) with no neutralization of the particles. Adsorption of the organo-cation on Egyptian bentonite, Volclay KWK and Pure-Flo B80, was above the CEC of the bentonites, yielding neutral and even slightly positively charged particles. Electron microscopy and X-ray diffraction results showed expansion of the basal spacing of the smectite. Such low-cost organo-bentonites might be suitable for environmental applications as removal of pollutants, drug and pesticides delivery, or water treatment. Application in turbidity reduction of industrial effluents is demonstrated.     

Minimizing crosstalk in three-axial induction magnetometers

A model for crosstalk in three-axial induction magnetometers has been developed theoretically and verified experimentally. The effect of crosstalk on the magnetometer accuracy has been analyzed. It has been found that the inevitable crosstalk in the transverse coils has two components: one due to the applied magnetic flux and the other due to the secondary flux produced by the electric current in the longitudinal coil. The first component has a constant magnitude. The phase of the second component, relative to the first one, is nearly 180° at low frequencies, 90° at resonance, and 0° at high frequencies. Its magnitude approaches zero at low frequencies, has the maximum at resonance, and then drops off by a factor equal to the coils' quality factor and approaches the first component value. As a result, the crosstalk due to the applied flux is dominant at low frequencies. At a frequency just below the resonance, the crosstalk is very low, if no magnetic feedback is applied. Just above the resonance, the crosstalk reaches the maximum because of the rapid increase in the secondary flux. Applying a strong enough magnetic feedback nearly flattens the crosstalk amplitude response. However, an undesirable effect of the feedback is that it significantly increases the minimum crosstalk value. A very low crosstalk at a single frequency can be beneficial for magnetometers tuned to a narrow frequency band. It can also be beneficial for wide-band magnetometers to measure their mechanical orthogonality with a minimum effect of crosstalk.     

The impact of cemented layers and hardpans on oxygen diffusivity in mining waste heaps A field study of the Halsbrücke lead-zinc mine tailings (Germany)

This article reports fibre-optic oxygen measurements on a reactive mine waste heap located in the polymetallic sulphide mine district of Freiberg in south-eastern Germany. The heaped material consists of sulphide-bearing tailings from a processing plant of a lead-zinc mine. Mine waste material was deposited in the water phase after separation of mining ores in a flotation process. The tailing impoundment is partly covered with coarse sand and topsoil. Oxygen profiles were monitored during one year at eleven locations showing different physical and mineralogical compositions. At each location a borehole was drilled where the optic sensors were installed at 2-5 different depths. After installation the oxygen profiles were monitored seven times during one year from 2006-2007 and three to five oxygen profiles at each location were obtained. Oxygen measurements were accompanied by physical, chemical and mineralogical data of the tailing material. Additionally, a detailed mineralogical profile was analysed at a location representative for the central part of the heap, where the cemented layers show lateral continuity. Results showed that cemented layers have a significant influence on natural attenuation of the toxic As and Pb species owing to their capacity of water retention. The measured oxygen profiles are controlled by the zone of active pyrite weathering as well as by the higher water content in the cemented layers which reduces gaseous atmospheric oxygen supply. In contrast, gypsum bearing hardpans detected at three other locations have no detectable influence on oxygen profiles. Furthermore, the grain size distribution was proved to have a major effect on oxygen diffusivity due to its control on the water saturation. Temporal changes of the oxygen profiles were only observed at locations with coarse sediment material indicating also an important advective part of gas flux.     

Using the KBTA method for inferring computer and network security alerts from time-stamped,raw system metrics

In this study, we propose a new approach for detecting previously unencountered instances of known classes of malicious software based on their temporal behavior. In the proposed approach, time-stamped security data are continuously monitored within the target computer system or network and then processed by the knowledge-based temporal abstraction (KBTA) methodology. Using KBTA, continuously measured data (e.g., the number of running processes) and events (e.g., installation of a software) are integrated with a security-domain, temporal-abstraction knowledge-base (i.e., a security ontology for abstracting meaningful patterns from raw, time-oriented security data), to create higher-level, time-oriented concepts and patterns, also known as temporal abstractions. Automatically-generated temporal abstractions can be monitored to detect suspicious temporal patterns. These patterns are compatible with a set of predefined classes of malware as defined by a security expert employing a set of time and value constraints. The new approach was applied for detecting worm-related malware using two different ontologies. Evaluation results demonstrated the effectiveness of the new approach. The approach can be used for detecting other types of malware by updating the security ontology with new definitions of temporal patterns.     

Approximating the Degree-Bounded Minimum Diameter Spanning Tree Problem

We consider the problem of finding a minimum diameter spanning tree with maximum node degree $B$ in a complete undirected edge-weighted graph. We provide an $O(\sqrt{\log_Bn})$-approximation algorithm for the problem. Our algorithm is purely combinatorial, and relies on a combination of filtering and divide and conquer.     

Natural convection in porous triangular enclosures with a solid adiabatic fin attached to the horizontal wall

A numerical analysis has been performed to investigate the effects of fin location onto the bottom wall of a triangular enclosure filled with porous media whose height base ratio is 1. The temperature of the bottom wall is higher than that of the inclined wall while the vertical wall is insulated. Thus, the fin divides the heated bottom wall to two separate regions. Finite difference method was applied to solve governing equations which are written using Darcy method. Solutions of algebraic equations were made by Successive Under Relaxation (SUR) technique. The effective parameters on flow and temperature fields are: Rayleigh number, location center of fin, dimensionless fin height, and dimensionless fin width. The obtained results indicated that the fin can be used as a control element for heat transfer and fluid flow.     

Interfacing the Cell with “Biomimetic Membrane Proteins”

Integral membrane proteins mediate a myriad of cellular processes and are the target of many therapeutic drugs. Enhancement and extension of the functional scope of membrane proteins can be realized by membrane incorporation of engineered nanoparticles designed for specific diagnostic and therapeutic applications. In contrast to hydrophobic insertion of small amphiphilic molecules, delivery and membrane incorporation of particles on the nanometric scale poses a crucial barrier for technological development. In this perspective, the transformative potential of biomimetic membrane proteins (BMPs), current state of the art, and the barriers that need to be overcome in order to advance the field are discussed.     

PdAlqEn: A Novel Upgraded Version of the PdEnCatTM Family of Polyurea Encapsulated Catalysts

Palladium nanoparticles are stabilized and encapsulated in a combination of polyurea and an ionic liquid (Aliquat 336) to obtain the PdAlqEn hybrid catalyst. The novel composite material is applied as a recyclable and robust catalyst in hydrogenation reactions.