Ageing and rejuvenation of Biopol™, [poly (3-hydroxybutyrate-co-3-hydroxyvalerate)] copolymers: A dielectric study

Semi-crystalline Biopol copolymers are biodegradable materials which are being intensively probed as suitable systems for embossed substrates in tissue regeneration applications. However, it has been shown that an embrittlement process occurs on storage at room temperature which places restrictions as to their application possibilities. In order to study this process we have made use of Biopol systems which have aged for 3 years since extrusion as thin films, and subsequently rejuvenated at elevated temperatures. Utilising varying techniques we have attempted to shed light on the mechanisms responsible for the rejuvenation, with particular emphasis on the observed dielectric properties. We highlight the possibility of on-going secondary crystallisation on ageing and attempt to rationalise the rejuvenation in terms of release of amorphous material from the rigid amorphous phase of semi-crystalline systems.     

Determination of phthalate ester congeners and mixtures by LC/ESI-MS in sediments and biota of an urbanized marine inlet

Phthalate esters (PEs) are a group of widely used commercial chemicals consisting of many different congeners. Concentrations of di(2-ethylhexyl) phthalate ester in the parts per million range have been observed in sediments from locations in North America and Europe. However, sediment and biota concentrations of other widely used PEs (i.e., dibutyl phthalate, diisononyl phthalate, and diisodecyl phthalate) are rare and often in doubt because of analytical difficulties. One of the problems is that commercial formulations predominantly consist of PEs with a specific molecular weight but include many isomers within each molecular weight class. Currently there are no analytical methods or required standards to fully separate PEs into the different molecular weight classes corresponding to the formulations from which they originate. Hence, ambient total and mixture-specific PE concentrations do not exist. This study presents a new method based on reversed-phase liquid chromatography/ electrospray ionization mass spectrometry (LC/ESI-MS) for the quantitative determination of individual PEs, including six congeners on the U.S. EPA Priority pollutant list and several commercial PE isomeric mixtures, in complex environmental matrixes. The method is applied to determine the composition of PE concentrations in sediments and fish in an urbanized marine ecosystem. PE fingerprints in sediments show a predominance of high molecular weight PEs and match per capita consumption levels of PEs. Fingerprints in fish tissue show a predominance of low molecular weight PEs and do not match per capita consumption levels. The findings indicate that the higher molecular weight PEs are less biologically available than the lower molecular weight ones.     

Analysis and observation of coupling ratio dependence of Rayleighbackscattering noise in a fiber optic gyroscope

Noise due to Rayleigh backscattering in a fiber-optic gyroscope is observed in quadrature with the Sagnac signal. This noise can be nulled by adjustment of the coupling ratio of the loop coupler and the state of polarization in the gyro loop. A rigorous analysis of the phases of, and the modulations applied to, the primary and scattered beams shows that no coherent Rayleigh backscatter noise should be detected on the Sagnac signal even with relatively coherent semiconductor laser sources     

Take a Closer Look: Emotion Modifies the Boundary Extension Effect.

Evidence has accumulated showing that central aspects of negative emotional scenes are remembered better than equivalent aspects of nonemotional scenes. Previous work, and an attentional account of these findings, led the authors to predict that anxiety-prone individuals would remember extremely negative emotional pictures as if seen from a closer perspective (i.e., with a less extended background) than other pictures. Findings showed that boundary extension was indeed reduced in high-trait-anxious individuals for very negative scenes, and this was more generally true for arousing scenes, with the exception of those with positive content. These findings are taken to be support for the view that attending to central aspects of emotionally arousing scenes can restrict the usual extended impression of surrounding space. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bigger than a breadbox? Attention to distractors may not enhance negative priming.

In several recent studies, P. A. MacDonald and colleagues (e.g., P. A. MacDonald and S. Joordens, 2000) reported unusually large negative priming effects and claimed that attention to distractors, counter to expectations, served to enhance the magnitude of the effect. In 3 experiments using their novel comparative judgment task, negative priming was assessed using both a control condition based on that of P. A. MacDonald, S. Joordens, and K. N. Seergobin (1999) and one in which control probe items exactly matched those on ignored repetition trials. In MacDonald et al.'s unmatched control condition, participants were faster than on ignored repetition trials, but this difference was reduced or absent when control items were matched. This result led to the conclusion that the apparently large negative priming effect reported by MacDonald and colleagues may be an artifact arising because judgments for a subset of their control trials were relatively easier than for ignored repetition trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the private sector in housing renewal: Lessons from the neighbourhood revitalisation services experiment in England

During the 1980s the British government made a number of attempts to involve the private sector in the administration and financing of housing renewal initiatives in inner city areas. One of the most significant of these was the Neighbourhood Revitalisation Services (NRS) initiative which was based on the Neighborhood Housing Services (NHS) concept developed in the United States. This paper traces the history of housing renewal policy in England leading up to the development of the NRS initiative. It then compares the NHS projects developed in the United States with the English NRS model and discusses the key differences. The performance of both the pilot NRS projects and the expanded programme of government‐funded NRS schemes is then examined in detail with particular emphasis upon the objective of involving private sector organisations in housing renewal. In conclusion the paper discusses the reasons why the NRS initiative failed to meet these objectives including those stemming from the differing housing and financial policy contexts in England and the United States. Ways are also suggested in which attempts to involve the private sector might be more successful in the future.     

Scanning Optical Microscopy via a Scanning Electron Microscope

We have described in detail the principles of operation of a commercially available SEM-based scanning optical microscope. The stage consists of a cathodoluminescent material which converts the scanning electron beam into a scanning optical beam and an optical system to focus the light beam onto the specimen. The resolution attainable with such a stage is discussed as well as the efficiency of electron-to-photon conversion. Simplified formulae are given and a set of curves plotted which can be used to determine the appropriate tradeoff between resolution and optical power. Examples of the imaging ability in the optical beam induced current mode from various semiconductor devices are presented.     

Distribution of phthalate esters in a marine aquatic food web: comparison to polychlorinated biphenyls

Dialkyl phthalate esters (DPEs) are widely used chemicals, with over 4 million tonnes being produced worldwide each year. On the basis of their octanol-water partition coefficients (Kow), which range from 10(1.61) for dimethyl phthalate to 10(9.46) for di-iso-decyl phthalate, certain phthalate esters have the potential to bioconcentrate and biomagnify in aquatic food webs. However, there are no reported field studies on the trophodynamics of phthalate ester in aquatic food webs. This study reports the distribution of 8 individual phthalate esters (i.e., dimethyl, diethyl, di-isobutyl, di-n-butyl, butylbenzyl, di(2-ethylhexyl), di-n-octyl, and di-n-nonyl) and 5 commercial isomeric mixtures (i.e., di-iso-hexyl (C6), di-iso-heptyl (C7), di-iso-octyl (C8), di-iso-nonyl (C9), and di-iso-decyl (C10)) in a marine aquatic food web. DPE concentrations were determined in 18 marine species, representing approximately 4 trophic levels. Co-analysis of DPEs and 6 PCB congeners (i.e., PCB-18, 99, 118, 180, 194, and 209) in all samples produced a direct comparison of the bioaccumulation behavior of PCBs and DPEs. Lipid equivalent concentrations of the PCBs increased with increasing trophic position and stable isotope ratios (delta15N). The Food-Web Magnification Factor (FWMF) of the PCB congeners ranged from 1.8 to 9.5. Lipid equivalent concentrations of low and intermediate molecular weight DPEs (i.e., C1-C7 DPEs: dimethyl, diethyl, di-iso-butyl, di-n-butyl, benzylbutyl, and C6 and C7 isomers) did not exhibit statistically significant trends with trophic position or stable nitrogen isotope ratios (delta15N) in the food web and FWMFs were not significantly different from 1. Lipid equivalent concentrations of the high-molecular-weight DPEs (i.e., C8-C10 DPEs: di(2-ethylhexyl), di-n-octyl, di-n-nonyl, C8, C9, and C10) declined significantly with increasing trophic position and stable isotope ratios (delta15N), producing FWMFs between 0.25 and 0.48. These results show that all DPEs tested did not biomagnify in the studied aquatic food web whereas PCBs did biomagnify.