A Weighted-Least-Squares Estimation Approach to Comparing Trends in Age-Adjusted Cancer Rates Across Overlapping Regions

Li and Tiwari (2008) recently developed a corrected Z-test statistic for comparing the trends in cancer age-adjusted mortality and incidence rates across overlapping geographic regions, by properly adjusting for the correlation between the slopes of the fitted simple linear regression equations. One of their key assumptions is that the error variances have unknown but common variance. However, since the age-adjusted rates are linear combinations of mortality or incidence counts, arising naturally from an underlying Poisson process, this constant variance assumption may be violated. This paper develops a weighted-least-squares based test that incorporates heteroscedastic error variances, and thus significantly extends the work of Li and Tiwari. The proposed test generally outperforms the aforementioned test through simulations and through application to the age-adjusted mortality data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute.     

Polypropylene-elastomer (TPO) nanocomposites: 2. Room temperature Izod impact strength and tensile properties

Room temperature Izod impact strength was determined for polypropylene (PP)/ethylene-co-octene elastomer (EOR) blends and nanocomposites, containing organoclays based on montmorillonite (MMT), at fixed elastomer content of 30 wt% and 0-7 wt% MMT. A ratio of maleated polypropylene, PP-g-MA to organoclay of unity was used as a compatibilizer in the nanocomposites. The organoclay serves to reduce the size of the EOR dispersed phase particles and facilitates toughening. The Izod impact strength is also influenced by the molecular weight of PP, elastomer octene content, elastomer MFI in addition to MMT content. Nanocomposites based on a low molecular weight polypropylene (L-PP) containing a higher octene content elastomer showed higher impact strength at lower MMT contents compared to those based on a low octene content elastomer. The effect of elastomer octene content on impact strength of high molecular weight polypropylene (H-PP) nanocomposites is not so significant. Elastomers having a melt flow index (MFI) in the range of 0.5-1.0 showed significant improvement in the impact strength of L-PP based nanocomposites. Most H-PP/EOR blends gave ‘super-tough’ materials without MMT and maintain this toughness in the presence of MMT. The critical elastomer particle size below which the toughness is observed is reduced by decreasing the octene content of the elastomer. For the similar elastomer particle sizes in nanocomposites, the impact strength varies as H-PP > M-PP > L-PP. The tensile modulus and yield strength improved with increasing MMT content; however, elongation at break was reduced. The extruder-made TPO showed a good-balance of properties in the presence of MMT compared to reactor-made TPO having similar modulus and elastomer content.     

Scalable synthesis of aligned carbon nanotubes bundles using green natural precursor: neem oil

Practical application of aligned carbon nanotubes (ACNTs) would have to be determined by a matter of its economical and large-scale preparation. In this study, neem oil (also named Margoaa oil, extracted from the seeds of the neem--Azadirachta indica) was used as carbon source to fabricate the bundles of ACNTs. ACNTs have been synthesized by spray pyrolysis of neem oil and ferrocene mixture at 825°C. The major components of neem oil are hydrocarbon with less amount of oxygen, which provided the precursor species in spray pyrolysis growth of CNTs. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterized through Raman spectroscopy, scanning and transmission electron microscopic (SEM/TEM) techniques. SEM images reveal that the bundles of ACNTs are densely packed and are of several microns in length. High-resolution TEM analysis reveals these nanotubes to be multi-walled CNTs. These multi-walled CNTs were found to have inner diameter between 15 and 30 nm. It was found that present technique gives high yield with high density of bundles of ACNTs.     

Cure characteristics,swelling behaviors,and mechanical properties of carbon black filler reinforced EPDM/NBR blend system

The effect of carbon black fillers viz. semireinforcing furnace (SRF), high abrasion furnace (HAF) and intermediate super abrasion furnace (ISAF) carbon blacks on the cure, swelling and mechanical properties of 70/30 EPDM/NBR blend have been investigated. The maximum torque values have been found to be increased with increase in filler loading. Filledsystems have been found to exhibit a reduced solvent uptake tendency compared to the unfilled sample. Blends loaded with ISAF exhibited the lowest toluene uptake among the carbon black filled systems due to the better filler reinforcement. A more uniform morphology has been observed for ISAF‐filled samples compared to the other filler loaded systems. The improvement in the mechanical properties has been observed to be the highest for ISAF‐filled samples followed by HAF and SRF filled systems. This has been attributed to the smaller particle size of ISAF black. The experimental results of mechanical testing have been compared with various theoretical models. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Role of interface on dynamic modulus of high‐performance poly(etheretherketone)/ceramic composites

High‐performance printed circuit board or electronic packaging substrate with low warping particularly at high frequency is the key demand of manufacturers. In the present work, poly(etheretherketone) (PEEK) matrix composites reinforced with untreated micron size aluminum nitride (AlN) and alumina (Al₂O₃) particles have been studied for dynamic modulus in the temperature range varying from 30 to 250°C. At 48 vol % particles, the room temperature modulus of the PEEK/AlN composites increased by approximately fivefold (～ 23 GPa), whereas it increased by twofold for PEEK/Al₂O₃ composite. The reinforcing efficiency is more pronounced at higher temperatures. The significant improvement in modulus was attributed to the better adhesion between the matrix and the AlN particles. Scanning electron microscope (SEM) and Kubat parameter showed that the poor adhesion between the matrix and the Al₂O₃ particles resulted in comparatively smaller increase in modulus of PEEK/Al₂O₃, despite higher intrinsic modulus of Al₂O₃ than that of AlN. SEM showed almost uniform distribution of particles in the matrix. The experimental data were correlated with several theoretical models. The Halpin–Tsai model with ξ (xi) is equal to four correlates well up to 48 vol % AlN composites while ξ is equal to two correlates only up to 18 vol % Al₂O₃ composites. Guth–Smallwood model also correlates well up to 28 vol % AlN and 18 vol % Al₂O₃‐filled composites. Thereafter, data deviated from it due to the particles tendency to aggregate formation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photoluminescent and tough hydrogels from silk fibroin and polyacrylic acid complexed with europium

Biocompatible, tough, and photoluminescent hydrogels are highly desirable for biomedical applications in vivo. Herein, hybrid hydrogels prepared from silk fibroin (SF) and polyacrylic acid (PAA) and complexed with europium, named as SF-PAA-Eu³⁺ hydrogels, exhibit good comprehensive properties. Owing to the intensive molecular interactions among SF, PAA, and Eu³⁺, SF-PAA-Eu³⁺ hydrogels show a greatest tensile strength of 0.58 MPa, elongation of 443%, and work of fracture of 1.65 MJ/m. In vivo imaging experiment in a mouse subcutaneous implantation model revealed excellent and sustained photoluminescence of the SF-PAA-Eu³⁺ hydrogels for 24 h. The work provides a strategy for designing functional SF-based hydrogels for imaging applications in vivo.     

Study on coke size degradation from coke plant wharf to blast furnaces stock house

The gas permeability, which is one of the most important requirements served by coke, is dependent largely on the size distribution of the coke at the various zones in the blast furnace. This papers deals with breakage of coke when it travels from wharf to blast furnace. In this study, six different coal blend samples in the range of 23.6–25.0% volatile matter and 11.7–14.8% ash were studied in stamp charged coke making process (wet bulk density 1.15 t/m³). The coke samples were collected from battery no. 8 wharf, CK06 (conveyer belt) and auto sampler. All experiments were conducted on shatter machine and an attempt has been made to find out reasons for breakage of coke. Results indicate that the coke size degradation is function of transporting system and dropping height of coke from wharf to blast furnace. It was also found that in stamp charging condition, it is possible to improve yield of blast furnace grade coke even at higher composition balance index of coal blend (2.94–3.70).     

Electrospinning pure protein solutions in core–shell fibers

Electrospinning of protein‐loaded fibers faces many challenges, e.g. burst release owing to segregation of the protein on the fiber surface, loss of activity due to electrospinning conditions, limitation of loading capacity etc. Core–shell electrospinning provides an effective way to electrospin fibers wherein the core can be loaded with bioactive molecules in friendly conditions of a compatible polymer solution, thereby protecting the molecules from the electrostatic field and organic solvent of shell solutions. The shell polymer, after the electrospinning, acts as a barrier to control the release of the loaded molecules. However, the limitation of loading capacity still remains due the prerequisite of using an additional polymer as additive to achieve the minimum viscosity of the core solution required for viscous drag by the shell solution being drawn by the electrostatic force. The work reported here aims to alleviate the need of a polymer additive by using aqueous protein solutions of very high concentration. High concentrations of protein solutions were successfully electrospun as the core of the protein–poly(lactide‐co‐glycolic acid) core–shell fibers. A partitioning effect was seen in the controlled release of hydrophilic proteins as they were retained in the aqueous core for longer times. Using lysozyme as a model protein, it was shown that the activity is significantly retained after electrospinning, compared with electrospinning in monolithic fibers. Moreover, the lysozyme activity was also comparable with the lysozyme released from core–shell fibers spun using poly(vinyl acetate) as additive in the core. Copyright © 2012 Society of Chemical Industry     

Sustainable conducting polymer composites: study of mechanical and tribological properties of natural fiber reinforced PVA composites with carbon nanofillers

ABSTRACT

Ball milled jute fiber (JF) was added to Polyvinyl Alcohol (PVA)/20 wt.% multi-layer graphene (MLG) composites in various proportions (0, 5, 10, 15 and 20 wt.%) to prepare sustainable and biodegradable conducting polymer composites. Also, PVA/17.5wt.%MLG/2.5wt.%MWCNT/20wt.% JF composite was prepared for comparison purpose. A dynamic mechanical analysis of the composites was conducted to analyze their viscoelastic nature. The electrical conductivity of the composites was measured to study their suitability for various applications. Jute reinforcement increased the electrical conductivity of PVA/MLG nanocomposites. The PVA/20wt.%JF/17.5wt.%MLG/2.5wt.%MWCNT hybrid composite had the highest electrical conductivity of 3.64 × 10^?4 S/cm among all the composites prepared. Multilayered structures of the hybrid composite films were made by hot-pressing, and their effectiveness in electromagnetic interference shielding was tested. The shielding effectiveness of the composites decreased with jute addition. The wear resistance of PVA/MLG/JF composites increased with an increase in the jute content up to an optimum value of 10 wt.%, and then it started deteriorating.     

The critical organic modifier aliphatic tail length for the formation of poly(methyl methacrylate)-montmorillonite nanocomposites

In this article, we report the influence of organic modifier structure (alkyl chain length C8-C20, single vs ditallow) and thereby, the effect of hydrophobicity on the structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)-clay hybrids. Melt processed PMMA-clay hybrids were characterized using wide-angle X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The organoclays having an alkyl chain length of more than 12 CH₂ groups resulted in the formation of nanocomposites. The glass transition temperature (T_g) of PMMA increased in the presence of clay. The mean-field lattice model was used to predict the free energy for nanocomposite formation, which showed a reasonable match with the experimental results and provided a general guideline for the proper selection of polymer and organoclay (ie, organic modifier) to obtain nanocomposite. Tensile modulus showed maximum improvement of 58% for the nanocomposites compared to 9% improvement for the composites. Tensile modulus increased with increases in the alkyl chain length of the organic modifier and clay loading. The level of improvement for the tensile properties of nanocomposites prepared from primary and secondary ammonium-modified clay is the same as that obtained with the commercial organoclays.