Impact of Ni co-implantation on Si nanocrystals formation and luminescence

We investigate the Si nanocrystals (Si-nc) growth and photoluminescence (PL) obtained by Si and Ni co-implantation. After 1 h of annealing at 1000 °C, PL emission between 600 and 1000 nm is observed to be five times higher for samples containing 0.04–0.21 at.% Ni than for samples without Ni. For samples annealed at 1100 °C, a small increase in PL intensity is observed followed by a decrease for Ni contents above 0.3 at.%. Our results are well described by a simple model which assumes that Ni atoms act both as a nucleation center for amorphous Si (a-Si) clusters crystallisation and as a non-radiative recombination site when more than one atom is included in a Si-nc. The nucleation effect is supported by the increase in PL intensity, the increase of PL decay time and the decrease of the a-Si Raman peak intensity at 480 cm^?1 for samples annealed at 1000 °C in presence of ～0.1 at.% Ni. Time-resolved PL shows that Ni mainly affects two emission bands. The first band, around 730 nm, is related to an oxygen surface state, suggesting that Ni enhances oxygen bonding with Si-nc. The second band, around 880 nm, is associated to the crystallisation effect induced by Ni at lower annealing temperature.     

The protection of mild steel by zinc-rich paint in flowing aerated 0.5 M NaCl solution—II. The effect of exposed area ratio

Experiments were performed in aerated 0.5 M NaCl solution over a range of selected Re numbers, using electrode couples of painted steel to bare steel at varying surface ratios. Results showed that, provided the painted to bare steel ratio was high flow, effects were not harmful. The bare steel was protected by a thin grey film of protective zinc hydroxide. Areas containing iron corrosion products were afforded temporary protection by a non-protective type of bulky white corrosion product, providing the steel was being subjected to cathodic protection. Once this was lost rusting of the underlying steel restarted at these points with iron corrosion products breaking through this overlying non-protective film.     

Innovative processes and technologies for modified atmosphere packaging of fresh and fresh-cut fruits and vegetables

Modified atmosphere packaging (MAP) technology has been commercially viable since the 1970s. Currently, MAP is extensively used worldwide to preserve the quality and extend the shelf-life of whole fresh fruits and vegetables, but is also increasingly used to extend the shelf-life of minimally processed fresh fruit and vegetables. This review discusses new processes and technologies that can be used to improve quality preservation and consumer acceptability of minimally processed produce where high respiration rates and challenging degradation processes operate. New packaging innovations are enabling producers and retailers to further maintain quality for longer. Innovative approaches to extend shelf-life include active MAP with differentially permeable films, films that incorporate antimicrobial properties, edible coatings that confer barriers properties, and the use of non-traditional gases to modify respiration. Intelligent packaging using integrated sensor technologies that can indicate maturity, ripeness, respiration rate and spoilage are also appearing. This review demonstrates that preservation technologies and associated packaging developments that can be combined with modified atmosphere are constantly evolving technology platforms. Adoption of combinations of technology improvements will be critical in responding to commercial trends towards more minimally processed fresh-cut and ready-to-eat fruit and vegetable products, which require specialized packaging solutions.     

Use of bacteriophages as biocontrol agents to control Salmonella associated with seed sprouts

Two Salmonella bacteriophages (SSP5 and SSP6) were isolated and characterized based on their morphology and host range, and evaluated for their potential to control Salmonella Oranienburg in vitro and on experimentally contaminated alfalfa seeds. Phages SSP5 and SSP6 were classified as members of the Myoviridae and Siphoviridae families, respectively. Both phages had a broad host range of over 65% of the 41 Salmonella strains tested. During in vitro trials, the phages resulted in incomplete lysis of Salmonella cultures, in spite of high levels of phage remaining in the system. Phage SSP5 was more effective in reducing Salmonella populations. Addition of phage SSP6 to alfalfa seeds previously contaminated with S. Oranienburg caused an approximately 1 log(10) CFU g(-1) reduction of viable Salmonella, which was achieved 3 h after phage application. Thereafter the phage had no inhibitory effect on Salmonella population growth. A second addition of the same (SSP6) or different (SSP5) phage to a Salmonella culture treated with phage SSP6, did not affect Salmonella populations. It was further shown that development of Salmonella permanently resistant to phage was not evident in either seed or in vitro challenge trials, suggesting the existence of a temporary, acquired, non-specific phage resistance phenomenon. These factors may complicate the use of phages for biocontrol.     

WEARING AWAY OF TANK BLOCKS1

A statement concerning the manner of the wearing away of tank blocks, factors affecting such wear, and detailed studies of surfaces of used tank blocks.     

芝加哥滨河步道扩建

<正>芝加哥河主干河道有着悠久且丰富的历史,它在很多方面映射了芝加哥城市的发展。芝加哥河以前是一条蜿蜒的沼泽溪流,后来被硬化改造为工程河道以支持城市向工业型的转换。1900年,为了改善公共卫生状况,城市将河流主干与南侧分支水流方向倒转。在此之后,此条河道声名鹊起。建筑师、城市设计师丹尼尔·伯纳姆提出了滨河散步道     

Crossing roads safely: an experimental study of age differences in gap selection by pedestrians

The over-representation of older pedestrians in serious injury and fatal crashes compared to younger adults may be due, in part, to age-related diminished ability to select gaps in oncoming traffic for safe road-crossing. Two experiments are described that examine age differences in gap selection decisions in a simulated road-crossing environment. Three groups of participants were tested, younger (30-45 years), young-old (60-69 years) and old-old (>75 years). The results showed that, for all age groups, gap selection was primarily based on vehicle distance and less so on time-of-arrival. Despite the apparent ability to process the distance and speed of oncoming traffic when given enough time to do so, many of the old-old adults appeared to select insufficiently large gaps. These results are discussed in terms of age-related physical, perceptual and cognitive limitations and the ability to compensate for these limitations. Practical implications for road safety countermeasures are also highlighted, particularly the provision of safe road environments and development of behavioural and training packages.