A Study of Composite Heuristic Algorithms

When faced with a difficult combinatorial problem whose optimization may be prohibitively expensive, researchers frequently turn to the study of fast heuristic algorithms in an effort to guarantee near-optimal results. An important aspect in the evaluation of such an algorithm is the determination of its worst-case behaviour, relative to an optimization rule. We here focus attention on schemes for combining two or more heuristics so as demonstrably to improve the worst case that can occur. We survey successful, illustrative examples of such composite algorithms, concentrating on problems of central significance from domains such as scheduling, packing and routeing. We also attempt to illuminate the conditions under which these strategies can be successful and why.     

Reductive cleavage of N-O bonds using Samarium(II) iodide in a traceless release strategy for solid-phase synthesis

A strategy for making amides and ureas using a polymer-supported hydroxylamine resin as a traceless linker is described. The cleavage of the linker by samarium(II) iodide is reported for the first time.     

Cigarette smoke extract induced protein phosphorylation changes in human microvascular endothelial cells in vitro

Phosphorylation is the most widely studied posttranslational modification (PTM) and is an important regulatory mechanism used during cellular responses to external stimuli. The kinases and phosphatases that regulate protein phosphorylation are known to be affected in many human diseases. Cigarette smoking causes cardiovascular disease (CVD). Endothelial cells play a pivotal role in CVD initiation and development; however, there have been limited investigations of the specific signaling cascades and protein phosphorylations activated by cigarette smoke in endothelial cells. The purpose of this research was to better understand the differential protein phosphorylation in endothelial cells stimulated with extracts of cigarette smoke total particulate matter (CS-TPM) in vitro. Human microvascular endothelial cells were exposed in vitro to CS-TPM at concentrations that were shown to cause endothelial cell dysfunction. The phosphorylated proteins were isolated using phosphoprotein-specific chromatography, followed by enzymatic digestion and nano-flow capillary liquid chromatography (ncap-LC) coupled to high resolution mass spectrometry. This study putatively identified 94 proteins in human microvascular endothelial cells that were differentially bound to a phosphoprotein-specific chromatography column following exposure to CS-TPM suggesting differential phosphorylation. Pathway analysis has also been conducted and confirmations of several observations have been made using immunoaffinity-based techniques (e.g., Western blotting). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Detection of autocatalytic decomposition behavior of energetic materials using APTAC

Characterization of autocatalytic decomposition reactions is important for the safe handling and storage of energetic materials. Isothermal differential scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition of energetic materials. However, isothermal DSC tests are time consuming and the choice of experimental temperature is crucial. This paper shows that an automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient screening tool for the identification of autocatalytic decomposition behavior of energetic materials. Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family. High concentrations of HAN are used as liquid propellants, and low concentrations of HAN are used primarily in the nuclear industry for decontamination of equipment. Because of its instability and autocatalytic decomposition behavior, HAN has been involved in several incidents.     

Fabrication of durable hydrophobic surfaces through surface texturing

Low surface energy polymer thin-films can be applied to surfaces to increase hydrophobicity and reduce friction for a variety of applications. However, wear of these thin films, resulting from repetitive rubbing against another surface, is of great concern. In this study, we show that highly hydrophobic surfaces with persistent abrasion resistance can be fabricated by depositing fluorinated carbon thin films on sandblasted glass surfaces. In our study, fluorinated carbon thin films were deposited on sandblasted and as-received smooth glass using deep reactive ion etching equipment by only activating the passivation step. The surfaces of the samples were then rubbed with FibrMet abrasive papers in a reciprocating motion using an automatic friction abrasion analyzer. During the rubbing, the static and kinetic friction forces were also measured. The surface wetting properties were then characterized using a video-based contact angle measuring system to determine the changes in water contact angle as a result of rubbing. Assessment of the wear properties of the thin films was based on the changes in the water contact angles of the coated surfaces after repetitive rubbing. It was found that, for sandblasted glass coated with fluorinated carbon film, the water contact angle remained constant throughout the entire rubbing process, contrary to the smooth glass coated with fluorinated carbon film which showed a drastic decrease in water contact angle with the increasing number of rubbing cycles. In addition, the static and kinetic friction coefficients of the sandblasted glass were also much lower than those of the smooth glass.     

Ultrafast magneto-optics in nickel: magnetism or optics?

Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5-1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation.