The Ablation and Oxidation Behaviors of SiC Coatings on Graphite Prepared by Slurry Sintering and Pack Cementation

SiC coatings were generated on graphite using slurry sintering (SS) and pack cementation (PC). The samples’ ablation features were assessed by an oxyacetylene torch. The rates of mass ablation of the PC–SiC and SS–SiC coatings were approximated 2.17?×?10^?3 and 9.52?×?10^?3 g s^?1, respectively, decreased by 84.1 and 29.6% compared to the uncoated samples. It was mainly attributed to the formation of a SiO₂ layer on the surface. The continuous SiO₂ molten film formed via the PC–SiC oxidation generates a sealing mechanism which can be an obstacle against the oxygen diffusion and hinder more ablation. This is while discontinuous SiO₂ film formed from the thin SS–SiC cannot protect the graphite effectively. The non-isothermal oxidation test shows that without the SiC coating, the sample weight is lost largely from 25 to 1500 °C, and its weight loss was 2.2% after the TGA. However, after coating, the samples possessed excellent oxidation protection and weight losses of SS–SiC and PC–SiC coatings are down to 1.3 and 0.6%, respectively. The more oxidation of the graphite substrate occurred due to the formation of macrocracks in the coating during the TGA and also the formation of holes on SiO₂ glass layer owing to release of CO or CO₂.     

Terrorist targeting and energy security

Sudden, short-term disruptions seriously endangering energy security can be triggered by a variety of events—among them attacks by terrorists. This study investigates terrorist attack practices against energy infrastructures and discusses how we may understand them. Our results indicate that attacks against energy infrastructures are comparatively few. Also, we find no strong connection between the ideologies of various terrorist groups and their proclivity to attack. In addition, the highly disproportionate number of attacks in a handful of countries highlights the strong geographic concentration of attacks. To explain these findings, we analyze terrorist targeting incentives including intimidation levels, symbolism, attack feasibility, and concerns for stakeholders. We argue that terrorists in general have comparatively few incentives to attack energy supply infrastructures based on our assessment of these factors. Moreover, higher levels of terrorist incidents in states more prone to internal violent conflict may suggest stronger incentives to attack energy infrastructures. When outlining energy security policies, the low frequency of worldwide attacks coupled with the high concentration of attacks in certain unstable countries should be taken into consideration. Energy importing countries could benefit from developing strategies to increase stability in key energy supply and/or transit countries facing risks of internal instability.     

Growing Innovative Calcium Carbonate Morphologies by Utilizing the Colloidal Gas Aphron System as a Surfactant-Based Template Method

Many studies have been conducted to study the various polymorphs and morphologies of calcium carbonate crystals in nature and living organisms. In this experimental work, a novel method has been employed to crystallize calcium carbonate by using colloidal gas aphron dispersion. The polymorph and morphology of prepared particles were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrometry techniques. SEM and XRD analyses demonstrated that the morphology of synthesized CaCO₃ can be changed from spherical (vaterite phase) to novel rod and plate-like shapes (mixture of vaterite and calcite phases) with changes in the surfactant concentration. The quantitative examination results of different calcium carbonate polymorph orientations showed that the precursor concentrations had no significant effect on the orientation of calcite phase, but rather they affected the orientation development of vaterite phase at a higher surfactant concentration.     

Awareness of faces is modulated by their emotional meaning.

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of perceptual load on attention-induced motion blindness: The efficiency of selective inhibition.

Recent visual marking studies have shown that the carry-over of distractor inhibition can impair the ability of singletons to capture attention if the singleton and distractors share features. The current study extends this finding to first-order motion targets and distractors, clearly separated in time by a visual cue (the letter X). Target motion discrimination was significantly impaired, a result attributed to the carry-over of distractor inhibition. Increasing the difficulty of cue detection increased the motion target impairment, as distractor inhibition is thought to increase under demanding (high load) conditions in order to maximize selection efficiency. The apparent conflict with studies reporting reduced distractor inhibition under high load conditions was resolved by distinguishing between the effects of "cognitive" and "perceptual" load. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A study of the evolution of the constituent phases and magnetic properties of hydrogen-treated Sr-hexaferrite during calcination

A hydrogen treatment followed by calcination, has been developed in order to enhance the intrinsic coercivity of Sr-hexaferrite (SrFe₁₂O₁₉). Fully hydrogen-treated Sr-hexaferrite consists of a mixture of 73%, by weight, of Fe and 27% of Sr₇Fe₁₀O₂₂ phases. Calcination of this material to reform the SrFe₁₂O₁₉ phase occurs in two stages. Between room temperature and 600°C, oxygen was absorbed resulting in a large increase in weight with the formation of a mixture of SrFeO_3–x and Fe₂O₃( and ). During the second stage, the intermediate phases reacted to form SrFe₁₂O₁₉ at a temperature of between 700 and 800°C. A partial desorption of oxygen occurred until calcination reached completion at 1000°C. The magnetization at 1100 kA m^–1 and the remanence were similar to those of the untreated material, but, because of a much refined grain size, the intrinsic coercivity was considerably larger, with values around 400 kA m^–1. Grain growth occurs at temperatures > 1000°C, resulting in a decrease in the intrinsic coercivity.     

A microfluidic platform using molecular beacon-based temperature calibration for thermal dehybridization of surface-bound DNA

This work presents a simple microfluidic device with an integrated thin-film heater for studies of DNA hybridization kinetics and double-stranded DNA melting temperature measurements. The heating characteristics of the device were evaluated with a novel, noninvasive indirect technique using molecular beacons as temperature probes inside reaction chambers. This is the first microfluidic device in which thermal dehybridization of surface-bound oligonucleotides was performed for measurement of double-stranded DNA melting temperatures with +/- 1 degrees C precision. Surface modification and oligonucleotide immobilization were performed by continuously flowing reagents through the microchannels. The resulting reproducibility of oligonucleotide surface densities, at 9% RSD, was better than for the same modification chemistries on glass slides in unstirred reagent solutions (RSD=20%). Moreover, the surface density of immobilized DNA probe molecules could be varied controllably by changing the concentration of the reagent solution used for immobilization. Thus, excellent control of surface characteristics was made possible, something which is often difficult to achieve with larger devices. Solid-phase hybridization reactions, a fundamental aspect of microarray technologies often taking several hours in conventional systems, were reduced to minutes in this device. It was also possible to determine forward rate constants for hybridization, k. These varied from 820,000 to 72,000 M(-1) s(-1), decreasing as surface densities increased. Surface densities could therefore be optimized to obtain rapid hybridization using such an approach. Taken together, this combined microfluidic/small-volume heating approach represents a powerful tool for surface-based DNA analysis.