Subcritical drying of silica gels

Silica aerogel is a sol-gel prepared material characterized by high porosity and large inner surface area. Aerogels can be prepared with a high transparency and low thermal conductivity, giving a material excellent for application as transparent thermal insulator. The traditional route to prepare silica aerogels is by formation of an alcogel by hydrolysis and condensation of silicon alkoxides followed by supercritical drying in an autoclave at high pressure (–100 atm). Unfortunately, this process is expensive and might be dangerous, so drying methods have been developed that operate under ambient conditions. In previous work, we have shown that gels can be strengthened and stiffened by providing new monomers to the alcogel giving xerogels with similar properties as aerogels by drying at ambient pressure (porosity up to 90%). This method of obtaining ambient pressure dried aerogels will be described and special emphasis will be given on the effect of the initial gel structure on the preparation of the xerogels.     

Nanocrystalline β-Ti alloy with high hardness,low Young's modulus and excellent in vitro biocompatibility for biomedical applications

High strength, low Young's modulus and good biocompatibility are desirable but difficult to simultaneously achieve in metallic implant materials for load bearing applications, and these impose significant challenges in material design. Here we report that a nano-grained β-Ti alloy prepared by high-pressure torsion exhibits remarkable mechanical and biological properties. The hardness and modulus of the nano-grained Ti alloy were respectively 23% higher and 34% lower than those of its coarse-grained counterpart. Fibroblast cell attachment and proliferation were enhanced, demonstrating good in vitro biocompatibility of the nano-grained Ti alloy, consistent with demonstrated increased nano-roughness on the nano-grained Ti alloy. Results suggest that the nano-grained β-Ti alloy may have significant application as an implant material in dental and orthopedic applications.     

Atomic‐Scale Control of Electronic Structure and Ferromagnetic Insulating State in Perovskite Oxide Superlattices by Long‐Range Tuning of BO6 Octahedra

Control of BO₆ octahedral rotations at the heterointerfaces of dissimilar ABO₃ perovskites has emerged as a powerful route for engineering novel physical properties. However, its impact length scale is constrained at 2–6 unit cells close to the interface and the octahedral rotations relax quickly into bulk tilt angles away from interface. Here, a long‐range (up to 12 unit cells) suppression of MnO₆ octahedral rotations in La_0.9Ba_0.1MnO₃ through the formation of superlattices with SrTiO₃ can be achieved. The suppressed MnO₆ octahedral rotations strongly modify the magnetic and electronic properties of La_0.9Ba_0.1MnO₃ and hence create a new ferromagnetic insulating state with enhanced Curie temperature of 235 K. The emergent properties in La_0.9Ba_0.1MnO₃ arise from a preferential occupation of the out‐of‐plane Mn d_3z²_?r² orbital and a reduced Mn e_g bandwidth, induced by the suppressed octahedral rotations. The realization of long‐range tuning of BO₆ octahedra via superlattices can be applicable to other strongly correlated perovskites for exploring new emergent quantum phenomena.     

Gold anion catalysis of methane to methanol

The oxidation of CH₄ has been investigated in the presence and absence of the atomic Au⁻ ion catalyst. We have employed the first principles density functional theory (DFT) and dispersion-corrected DFT calculations for the transition state on the Au⁻ ion and analyzed the thermodynamics properties of the reactions as well. Our results demonstrate that atomic gold anions could be used to catalyze CH₄ into valuable industrial products without the emission of CO₂, thereby making gold extremely valuable. The fundamental mechanism involves breaking the C–H bond through the formation of the anionic Au⁻(CH₄) molecular complex permitting the oxidation of CH₄ to methanol at the temperature of 325 K which is below that of CO₂ emission. Potentially, this could significantly impact the quality of our environment.     

Evaluation and suitability of biomaterials for modified atmosphere packaging of fresh salmon fillets

An evaluation of the suitability of commercially available biopolymers on the shelf‐life of fresh salmon fillet was done. The comparison included two different types of biomaterials, poly lactic acid (PLA)‐based and starch‐based materials, and two traditional materials, amorphous polyethylene terephthalate/polyethylene (APET/PE) and high‐density polyethylene (HDPE). Fresh salmon fillets were stored at 4°C in modified atmosphere (60% CO₂ and 40% N₂) for 5, 7, 9 and 14 days. The biomaterials have been briefly evaluated with respect to composition and mechanical properties. The effect of different packaging materials on bacterial growth, off‐odour, pH and colour was investigated. The traditional materials (APET/PE and HDPE trays) offered the best protection regarding the bacterial growth. A relatively high level (log 6 CFU/g) of total viable counts was detected after 9 days and 14 days for fillets stored in biomaterials and traditional materials, respectively. The level of lactic acid bacteria and H₂S producing bacteria followed almost the same pattern. Storage in traditional materials resulted in higher intensity of freshness (fresh odour) compared with the samples stored in biomaterials; after 14 days, the salmon stored in starch‐based pouches was regarded as having lower intensity of freshness compared with APET/PE trays and PLA‐based pouches. The opposite result was obtained regarding the colour of the salmon, where the biomaterials resulted in higher intensity of fresh colour compared with the traditional materials although the surface of the salmon at the end of the experiment was dry and unpleasant. Copyright © 2011 John Wiley & Sons, Ltd.     

Structural brain correlates of verbal and nonverbal fluency measures in Alzheimer's disease.

This study examined the relationships between regional brain volumes and semantic, phonological, and nonverbal fluency in 32 participants with Alzheimer's disease (AD). Object but not animal semantic fluency correlated with frontal and temporal gray matter volumes. Phonological fluency was not significantly associated with any brain volume examined. Nonverbal fluency was selectively associated with bilateral frontal gray matter volumes. Hippocampal volumes, although markedly reduced in these patients, were not related to any of the fluency measures. Results lend evidence to the importance of the frontal lobes in the directed generation of nonverbal and verbal exemplars by AD patients. Furthermore, both left and right-hemisphere regions contribute to the generation of verbal and nonverbal exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebellar volume decline in normal aging, alcoholism, and Korsakoff's syndrome: Relation to ataxia.

The authors used magnetic resonance imaging to measure gray and white matter volumes in cerebellar hemispheres and 4 vermian regions in 61 normal control (NC) men aged 23–72 years, 25 men with uncomplicated alcoholism (ALC), and 8 men and 1 woman with alcoholic Korsakoff's syndrome (KS). NC and ALC took quantitative gait and balance tests. Gray but not white matter volume declined with normal age in both hemispheres and anterior–superior vermis. ALC had gray but not white matter cerebellar hemisphere volume deficits, whereas KS had deficits in both tissue types. ALC and KS had gray and white matter volume deficits in anterior superior but not posterior inferior vermis. ALC had a 1 SD ataxia deficit, significantly and selectively correlated with white matter volume in anterior superior vermis. Regional distribution but not severity of cerebellar volume deficits is similar in alcoholic individuals whether or not complicated by KS and relates to ataxia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic fire detection in road traffic tunnels

Fire detection experiments in a road traffic tunnel were performed in the Runehamar test tunnel 5th–8th March 2007. The Runehamar test tunnel is a full profile road traffic tunnel, 1.65 km long, located outside Åndalsnes, Norway. The goal was to examinate smoke and heat detection systems to determinate what kind of principle best suited for detecting a fire in an early stage. The systems were tested during small Heptane pool fires, varying between 0.16 m² and 1 m², giving heat release rates from 0.2 MW to 2.4 MW accordingly, and one car fire of about 3–5 MW, and with wind conditions varying from 1.1 m s^?1 to 1.6 m s^?1. The size of the fires, were designed to be in the range from impossible to difficult to detect. The results were conclusive. Earliest detection of a car fire, fire starts inside, was by smoke detection given fixed limits (3000 μg m^?3). With open pool fires, or immediate flames, continues fibre optical heat detection systems was faster given the limits 3 °C/4 min.     

A Comparative Study of Boundary Control With First- and Second-Order Switching Surfaces for Buck Converters Operating in DCM

A performance comparison of boundary control with the first-(sigma¹) and second-order(sigma²) switching surfaces for buck converters operating in discontinuous conduction mode (DCM) is presented in this paper. Performance attributes under investigation include the average output voltage, output ripple voltage, switching frequency, parametric sensitivities to the component values, and large signal characteristics. Due to the presence of the output hysteresis band, an additional switching boundary formed by the zero-inductor-current trajectory is created. This phenomenon causes a shift of the operating point in converters with sigma¹. Conversely, the operating point remains unchanged in converters with sigma². As well as in continuous conduction mode (CCM), sigma² can make the converter revert to the steady-state in two switching actions in DCM and gives better static and dynamic responses than in both CCM and DCM. Most importantly, its control law and settings are applicable for both modes. Experimental results of a prototype are found to be in good agreement with theoretical predictions.