Crack Healing in a Silicon Nitride Ceramic

A detailed study has been undertaken on crack healing at high temperatures in a silicon nitride containing 10 wt% additives in order to identify the dominant mechanism responsible for the phenomenon. Fracture toughness increased with annealing time and the crack growth rate decreased until arrest with increasing testing time. Differentiation between possible operating mechanisms was obtained using critical experiments involving detailed compliance measurements, crack wake removal, and crack reinitiation tests and a comprehensive TEM study of healed cracks. It was found that crack healing was not uniform in the crack wake. When the original crack path was either transgranular or intergranular, healing was associated with the appearance of a thin layer of silica glass due to the oxidation of Si₃N₄ grains. But when the crack went through multigrain junctions, the former crack path was completely obliterated and replaced by a new, crystalline phase formed by diffusion of the preexisting glass phase. It is concluded that the increased crack growth resistance and fracture toughness at high temperature is attributable to the partial recovery of the original strength from the crack segments at multigrain junctions due to vitreous phase flow and subsequent crystallization.     

Modeling Water Treatment Chemical Disinfection Kinetics

Various empirical and probabilistic kinetic inactivation models that can be used to assist in the design and analysis of potable water disinfection systems were reviewed. Models were derived for both disinfectant demand-free and demand conditions. Ozone was used to inactivate heterotrophic plate count bacteria that were grown in natural water under low nutrient conditions and enumerated using R2A agar at 20°C for 7 days. Experiments were conducted at 22°C in 0.05 M (pH 6.9) phosphate buffer in bench-scale, batch 250 mL reactors. This disinfection data set, characterized by tailing-off behavior, was used to assess Chick–Watson, Hom-type, Rational, Hom–Power law, and Selleck model fit to the observed logarithmic survival ratios. It was found that the Chick–Watson model did not adequately represent the ozone disinfection kinetics. A Hom-type model incorporating a first-order disappearance term for ozone residual was found to best describe the observed inactivation of heterotrophic plate count bacteria. Named the incomplete gamma Hom model, it was found to be a robust kinetic model. The proposed incomplete gamma Hom model can be used to generate simple design charts for a wide range of disinfectant types, organisms, and conditions, as an aid to the design of water disinfection systems.     

Ability of patients to recall habitual contact lens products and enhancement of recall using photographic aids

Purpose

To determine the proportion of soft contact lens (CL) wearers who are able to recall their habitual products (lenses and care system) correctly from memory, and to evaluate the value of using photographic aids (PAs) to improve recall.

Methods

103 soft lens wearers attended 2 visits to investigate their habitual CL product use. At the first visit they were asked to recall which products they were using and then to identify their products from PAs. They returned for a second visit with their products for confirmation.

Results

51% correctly reported their lens brands from memory alone, which improved to 87% with the use of the PAs (p < 0.001). 41% correctly reported their habitual care system from memory alone, which improved to 80% with the use of PAs (p < 0.001). Females were better at recalling care system brand names than males (49% versus 27% correct, p = 0.040) and wearers with more than 1 year experience with their habitual CLs had better recall than those with up to 1 year experience (63% versus 27%, p = 0.014).

Conclusion

Less than 50% of contact lens wearers were able to recall the names of their habitual lens and lens care products correctly from memory. PAs improved this recall significantly for both contact lenses and contact lens care systems.     

Cytotoxic and inflammatory effects of contact lens solutions on human corneal epithelial cells in vitro

Purpose

To ascertain the effect that four contact lens (CL) multipurpose solutions (MPS) have on the viability and release of pro-inflammatory cytokines from human corneal epithelial cells (HCEC).

Comfort properties of 3D-knitted seamless female body armour vests

This paper reports the comfort properties of 3D-knitted seamless female body armour vests evaluated by using a thermal manikin. The vests were designed as a complete garment with eliminating the conventional cutting and sewing, to improve fit and comfort for female police officers. The vests were tested on thermal manikin dressed with vests only and manikin dressed with a police officer’s uniform including the vests. Both dry thermal insulation and evaporative resistance were evaluated for comfort properties. The results showed that five-layer assembly of fitted-vest provided an acceptable level of thermal insulation. However, the evaporative resistance of the loose-vest showed better results compared to the fitted-vest, which was proved by the lower surface temperature on the thermal imaging. This research established that the 3D-knitted seamless body armour vests can provide an effective solution for the body armour requirement for female officers. The results also suggested that increasing the number of layers will increase the weight and reduced level of comfort, however they were effective in providing the necessary protection from low-level stab threats, which was shown in the earlier publication.     

Precise chemical analysis development for Si and GaAs surfaces

Precise chemical analysis (PCA) was developed to allow the study of non-interconnected atoms on crystalline semiconductor surfaces, such as those produced during rapid thermal processing (RTP) of silicon and electron beam lithography on gallium arsenide (GaAs). The PCA method is based on selectively dissolving the different components present on the semiconductor surface using preferential etchant solutions. After etching, the etchant solution, containing the etched component, is analyzed by a photometric technique. In this paper, we present photometric measurements of the amount of free (non-interconnected) atoms that remain on semiconductor surfaces following electron beam and RTP processing. In this context, free atoms are those presenting in any form other than crystalline GaAs or Si, for instance, those in the form of surface oxides. Using the PCA method, free Ga and As were detected on GaAs surfaces after electron beam lithography. Free silicon, boron and phosphorous atoms were found on silicon surfaces after RTP. The concentration of boron diffused into a silicon wafer during RTP was also carried out by means of slight surface etching. We estimate the accuracy of this PCA method at 2% for Ga and 5% for all other elements.     

The Theory of "truth": How Counterindustry Campaigns Affect Smoking Behavior Among Teens.

This study used structural equation modeling to test a theory-based model of the pathways by which exposure to the "truth" counterindustry media campaign influenced beliefs, attitudes, and smoking behavior in national random-digit-dial telephone surveys of 16,000 12- to 17-year-olds before, 8 months after, and 15 months after campaign launch. Consistent with concepts from the theory of reasoned action, youth in markets with higher levels of campaign exposure had more negative beliefs about tobacco industry practices and more negative attitudes toward the tobacco industry. Models also provided support for a social inoculation effect, because negative industry attitudes were associated with lower receptivity to protobacco advertising and with less progression along a continuum of smoking intentions and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ApoB siRNA-induced Liver Steatosis is Resistant to Clearance by the Loss of Fatty Acid Transport Protein 5 (Fatp5)

The association between hypercholesterolemia and elevated serum apolipoprotein B (APOB) has generated interest in APOB as a therapeutic target for patients at risk of developing cardiovascular disease. In the clinic, mipomersen, an antisense oligonucleotide (ASO) APOB inhibitor, was associated with a trend toward increased hepatic triglycerides, and liver steatosis remains a concern. We found that siRNA-mediated knockdown of ApoB led to elevated hepatic triglycerides and liver steatosis in mice engineered to exhibit a human-like lipid profile. Many genes required for fatty acid synthesis were reduced, suggesting that the observed elevation in hepatic triglycerides is maintained by the cell through fatty acid uptake as opposed to fatty acid synthesis. Fatty acid transport protein 5 (Fatp5/Slc27a5) is required for long chain fatty acid (LCFA) uptake and bile acid reconjugation by the liver. Fatp5 knockout mice exhibited lower levels of hepatic triglycerides due to decreased fatty acid uptake, and shRNA-mediated knockdown of Fatp5 protected mice from diet-induced liver steatosis. Here, we evaluated if siRNA-mediated knockdown of Fatp5 was sufficient to alleviate ApoB knockdown-induced steatosis. We determined that, although Fatp5 siRNA treatment was sufficient to increase the proportion of unconjugated bile acids 100-fold, consistent with FATP5's role in bile acid reconjugation, Fatp5 knockdown failed to influence the degree, zonal distribution, or composition of the hepatic triglycerides that accumulated following ApoB siRNA treatment.