Ultrasonic relaxation studies of poly(isobutylene) in m-xylene

Ultrasonic measurements are reported on solutions of two different samples of poly(isobutylene), one relatively regularCH₂C(CH₃)₂(Vistanex L80) and one with considerable structural irregularity such as chain branching (Vistanex L140). Measurements were carried out from 303–353K in m-xylene over a frequency range 1–100 MHz. A low frequency normal mode (viscoelastic) and a higher frequency conformational absorption are observed. The temperature dependence of the conformational absorption reveals a pseudo helix-coil transition at around 323K. Above this temperature, the two polymers show temperature coefficients of different sign. This phenomenon is explained in terms of a lower energy difference between conformational states in the branched chain polymer.     

JOINT HYPOTHESIS TESTS FOR A RANDOM WALK BASED ON INSTRUMENTAL VARIABLE ESTIMATORS

Abstract. In this paper we propose test statistics for the null hypothesis of a random walk or a random walk with drift for the case in which the innovations to the series are a moving-average process. The statistics are based on the instrumental variable estimators proposed by Hall and by Pantula and Hall and are shown to have the limiting distributions tabulated by Dickey and Fuller.     

Catalytic gasification of doped carbon — a microscopic study

Inorganic additives in carbons are often active, catalytically, during its gasification. The method of addition, particle size, chemical composition and subsequent heattreatment of the additives control their relative efficacies. There are difficulties in attempts to reproduce these efficacies. To overcome these problems, carbons have been prepared by carbonisation of the polymer prepared from furfuryl alcohol containing known concentrations of soluble additives. The resultant carbons contain atomic dispersions of metals in a manner analogous to doped semi-conductors. Such dispersions are catalytically active to gasification by CO₂, N₂O and O₂. Topographical changes produced on gasification are followed by scanning electron microscopy. Rarely, if ever, does the gasification proceed evenly over the entire surface. The resultant pitting can influence structural and adsorptive properties of commercial carbons, subject to gasification, i.e. parent materials for active carbons and cokes. Results indicate that diffusion of the catalytically active metal into carbon from catalytic material added in particulate form may be a significant stage in the mechanism of catalytic gasifications.     

Non-Isothermal Crystallization of Bovine Milk Fat

The crystallization kinetics of milk fat were studied under non-isothermal and simulated adiabatic conditions using pulsed NMR spectroscopy. Isothermal experiments confirmed that when milk fat is shock cooled to below the α melting point it crystallizes in two steps due to the different crystallization kinetics of α and β′ modifications. In non-isothermal experiments, the fat samples were heated early during the plateau between steps to a temperature above the α melting point and β′ crystals formed more rapidly than in isothermal conditions. Fresh α crystals are believed to melt and form lamellar units containing triglyceride molecules with high degrees of isomorphism and these units can accelerate the nucleation and growth rates of β′ polymorph crystals. The crystallization behavior changed when the heating occurred late in the plateau and the α crystals are believed to have demixed, which allowed them to transform to β′ crystals directly in the solid state. Under simulated adiabatic conditions the rate of β′ crystallization was increased by a factor of 2–3 over the isothermal case. These findings were used to infer approaches to process difficult fat blends in scraped-surface heat exchanger plants.     

Transcriptome Analysis in a Primary Human Muscle Cell Differentiation Model for Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is caused by CTG-repeat expansions leading to a complex pathology with a multisystemic phenotype that primarily affects the muscles and brain. Despite a multitude of information, especially on the alternative splicing of several genes involved in the pathology, information about additional factors contributing to the disease development is still lacking. We performed RNAseq and gene expression analyses on proliferating primary human myoblasts and differentiated myotubes. GO-term analysis indicates that in myoblasts and myotubes, different molecular pathologies are involved in the development of the muscular phenotype. Gene set enrichment for splicing reveals the likelihood of whole, differentiation stage specific, splicing complexes that are misregulated in DM1. These data add complexity to the alternative splicing phenotype and we predict that it will be of high importance for therapeutic interventions to target not only mature muscle, but also satellite cells.     

Optical Properties of Hydrothermally Synthesized Hematite Particulate Pigments

Iron oxide hematite particles with various shapes (platelet, polyhedron, pseudocube, and peanut-like) have been synthesized by hydrothermal treatment of a Fe(OH) _x O _y precursor under various conditions. The size and shape of hematite particles can be adjusted by carefully controlling the processing parameters such as holding time, temperature, and adsorption ions present in the system. The nearly monosized α-Fe₂O₃ platelets possess face diameters of approximately 3 μm and a thickness of 0.5 μm under a scanning electron microscope. The apparent color of the particles changes as particle size and shape varies. Munsell color notation was employed to compare the color of hematite particles with various sizes and shapes. Diffuse reflectance spectra show that a "red-shift" of 40 nm is observed in platelet, pseudocube, and peanut-like particles compared with conventional particles. The band at 850 nm for the ⁶A₁→⁴T₁ transition was split in the pseudocubic and peanut-like particles. Raman spectra of the hematite particles also reveal that the vibrational modes of α-Fe₂O₃ particles diminish as particle size decreases, and dependence of vibrational band intensity on frequency is also observed. The spectral profiles demonstrate significant difference as excitation radiation lines changes from blue (457 nm) to red (647 nm). Possible mechanisms responsible for the optical properties of hematite particles are postulated based on the findings of the experiments.     

An evaluation of the impact of exemptions to the children's sleepwear flammability standards on burn injuries to children

In 1996, the U.S. Consumer Product Safety Commission (CPSC) amended the children's sleepwear flammability standards to exempt sleepwear sized for infants aged nine months or younger and tight‐fitting sleepwear for older children. The amendments were developed in response to an apparent preference for untreated cotton garments by many parents and difficulties in enforcing the pre‐amendment standards. However, they were adopted only after CPSC concluded that they would provide consumers a wider selection of children's sleepwear without diminishing the protection provided by the pre‐amendment standards. The amendments became effective in 1997, but remained controversial, with some interested parties believing that the exemptions would substantially reduce the level of safety for children. To address these concerns, and in cooperation with the American Burn Association and Shriners Hospitals for Children, the CPSC initiated a national study of child clothing‐related burn injuries treated in burn center hospitals. From 2003 through 2005, the CPSC collected information on 475 such injuries. This study evaluates the burn center data to help determine the safety effects of the amendments to the sleepwear standards. The results provide no evidence of increased risk of burn injury associated with the exemptions from the sleepwear standards. Copyright © 2010 John Wiley & Sons, Ltd.     

Bioaffinity detection of pathogens on surfaces

The demand for improved technologies capable of rapidly detecting pathogens with high sensitivity and selectivity in complex environments continues to be a significant challenge that helps drive the development of new analytical techniques. Surface-based detection platforms are particularly attractive as multiple bioaffinity interactions between different targets and corresponding probe molecules can be monitored simultaneously in a single measurement. Furthermore, the possibilities for developing new signal transduction mechanisms alongside novel signal amplification strategies are much more varied. In this article, we describe some of the latest advances in the use of surface bioaffinity detection of pathogens. Three major sections will be discussed: (i) a brief overview on the choice of probe molecules such as antibodies, proteins and aptamers specific to pathogens and surface attachment chemistries to immobilize those probes onto various substrates, (ii) highlighting examples among the current generation of surface biosensors, and (iii) exploring emerging technologies that are highly promising and likely to form the basis of the next generation of pathogenic sensors.     

Low-Temperature Hydrothermal Synthesis of Yttrium-Doped Zirconia Powders

The feasibility of low-temperature synthesis of yttrium-doped zirconia (Y-ZrO₂) crystalline powders in aqueous solutions at lessthan equal to100°C has been evaluated, and the hydrothermal crystallization mechanism for Y-ZrO₂ powders also has been investigated. Coprecipitated (Y,Zr) hydroxide gel, mechanical mixtures of Y(OH)₃ and Zr(OH)₄ gel, and Y(OH)₃ gel have been reacted in boiling alkaline solutions. Coprecipitated (Y,Zr) hydroxide gel crystallized to cubic or tetragonal Y-ZrO₂ at pH 13.9. The yttrium content in the powder synthesized from coprecipitated (Y,Zr) hydroxide is consistent with the initial precursor solution composition, as expected from the similarity in solubility of Zr(OH)^-₅ and Y(OH)^-₄. A diffusionless mechanism for the transformation of the (Y,Zr) hydroxide gel to Y-ZrO₂ is proposed, and the phase stability in aqueous solution is discussed in terms of an in situ crystallization model. It is also demonstrated through thermodynamic arguments with experimental verification that the stable form of the Y-ZrO₂ at 25°C is the anhydrous phase, not the metal hydroxide as previously thought.