Hexabromocyclododecane: current understanding of chemistry, environmental fate and toxicology and implications for global management

Hexabromocyclododecane (HBCD) is a globally produced brominated flame retardant (BFR) used primarily as an additive FR in polystyrene and textile products and has been the subject of intensified research, monitoring and regulatory interest over the past decade. HBCD is currently being evaluated under the Stockholm Convention on Persistent Organic Pollutants. HBCD is hydrophobic (i.e., has low water solubility) and thus partitions to organic phases in the aquatic environment (e.g., lipids, suspended solids). It is ubiquitous in the global environment with monitoring data generally exhibiting the expected relationship between proximity to known sources and levels; however, temporal trends are not consistent. Estimated degradation half-lives, together with data in abiotic compartments and long-range transport potential indicate HBCD may be sufficiently persistent and distributed to be of global concern. The detection of HBCD in biota in the Arctic and in source regions and available bioaccumulation data also support the case for regulatory scrutiny. Toxicity testing has detected reproductive, developmental and behavioral effects in animals where exposures are sufficient. Recent toxicological advances include a better mechanistic understanding of how HBCD can interfere with the hypothalamic-pituitary-thyroid axis, affect normal development, and impact the central nervous system; however, levels in biota in remote locations are below known effects thresholds. For many regulatory criteria, there are substantial uncertainties that reduce confidence in evaluations and thereby confound management decision-making based on currently available information.     

Continuous Synthesis of Device‐Grade Semiconducting Polymers in Droplet‐Based Microreactors

A method is reported for the controlled synthesis of device‐grade semiconducting polymers, utilizing a droplet‐based microfluidic reactor. Using poly(3‐hexylthiophene) (P3HT) as a test material, the reactor is shown to provide a controlled and stable environment for polymer synthesis, enabling control of molecular weight via tuning of flow conditions, reagent composition or temperature. Molecular weights of up to 92 000 Da are readily attainable, without leakage or reactor fouling. The method avoids the usual deterioration in materials quality that occurs when conventional batch syntheses are scaled from the sub‐gram level to higher quantities, with a prototype five‐channel reactor producing material of consistent molecular weight distribution and high regioregularity (>98%) at a rate of ≈60 g/day. The droplet‐synthesized P3HT compares favorably with commercial material in terms of absorption spectrum, polydispersity, regioregularity, and crystallinity, yielding power conversion efficiencies of up to 4% in bulk heterojunction solar cells with [6,6]‐phenyl‐C61‐butyric acid methyl ester.     

Dietary exposure to chloropropanols of secondary school students in Hong Kong

This paper reports levels of 3-monochloropropan-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) in a wide range of food items and estimates their dietary exposure for secondary school students in Hong Kong. Dietary exposure to chloropropanols was estimated using local food consumption data obtained from secondary school students in 2000 and the concentrations of 3-MCPD and 1,3-DCP in food samples taken from the local market. The dietary exposure to 3-MCPD for an average secondary school student consumer was estimated to be 0.063–0.150 µg kg^?1 body weight (bw) day^?1, whilst that for the high consumer was 0.152–0.300 µg kg^?1 bw day^?1. Both estimates fell below the provisional maximum tolerable daily intake of 2 µg kg^?1 bw established by the Joint Expert Committee on Food Additives (JECFA) and amounted to less than 20% of this safety reference value. The dietary exposure to 1,3-DCP for an average secondary school student consumer was estimated to be 0.003–0.019 µg kg^?1 bw day^?1, whilst that for the high consumer was 0.009–0.040 µg kg^?1 bw day^?1. The resulting margins of exposures were of low concern for human health. It could be concluded that both the average and high secondary school student consumers were unlikely to experience major toxicological effects of 3-MCPD and 1,3-DCP.     

Routing in Distributed Cognitive Radio Networks: A Survey

Cognitive Radio Networks (CRNs) have been receiving significant research attention recently due to their ability to solve issues associated with spectrum congestion and underutilization. In a CRN, unlicensed users (or Secondary Users, SUs) are able to exploit and use underutilized licensed channels, but they must evacuate the channels if any interference is caused to the licensed users (or Primary Users, PUs) who own the channels. Due to the dynamicity of spectrum availability in CRNs, design of protocols and schemes at different layers of the SU’s network stack has been challenging. In this article, we focus on routing and discuss the challenges and characteristics associated with it. Subsequently, we provide an extensive survey on existing routing schemes in CRNs. Generally speaking, there are three categories of challenges, namely channel-based, host-based, and network-based. The channel-based challenges are associated with the operating environment, the host-based with the SUs, and the network-based with the network-wide SUs. Furthermore, the existing routing schemes in the literature are segregated into three broad categories based on the relationship between PUs and SUs in their investigation, namely intra-system, inter-system, and hybrid-system; and within each category, they are further categorized based on their types, namely Proactive, Reactive, Hybrid, and Adaptive Per-hop. Additionally, we present performance enhancements achieved by the existing routing schemes in CRNs. Finally, we discuss various open issues related to routing in CRNs in order to establish a foundation and to spark new interests in this research area.     

Characteristics of Er-doped Al2O3 thin filmsdeposited by reactive co-sputtering

Er-doped Al₂O₃ thin films have been deposited by reactive co-sputtering onto thermally oxidized Si-wafers. The deposition process has been optimized with respect to the requirements originating from the application of these multilayer structures as integrated optical amplifiers for the third telecom window, i.e., the wavelength range 1.52-1.55 μm. The films obtained at a substrate temperature of only 400°C are amorphous and show a homogenous structure, without columns or grains. For slabguides, background losses smaller than 0.25 dB/cm have been obtained, even without any annealing. A relatively broad luminescence band, having an FWHM of ~55 nm around the 1.533-μm wavelength, has been measured. From gain versus pumping power curves, an upconversion coefficient lower then 20·10^-25 m³/s has been derived, being half of the values reported up to now in the literature. Simulations based on experimentally determined material parameters and assuming a channel attenuation of 0.5 dB/cm indicate, for 0.24 at.% Er channel devices with an optimal channel length of 7.7 cm, an amplification of 8 dB at 1.533 μm for a pump wavelength of 1.48 μm, and a pump power of only 8.7 mW     

Reactive magnetron sputtering of indium tin oxide films on acrylics – morphology and bonding state

Indium tin oxide (ITO) films were deposited on acrylics by low temperature reactive magnetron sputtering. The effects of oxygen flow and bias voltage on the microstructure, surface morphology and bonding state of films were evaluated. In this investigation, X-ray photoelectron spectroscopy, X-ray diffraction, Atomic force microscope were used. It was found that the grain size of ITO films increased and surface roughness decreased with the increase of oxygen flow rate. The XPS spectra of In 3d and Sn 3d indicated that the oxygen flow had little effect on the binding energy of ITO films. The relative strength of O²⁻_II increased, while that of O²⁻_I decreased with increasing oxygen flow rate. The grain size increased with the bias voltage. However, at a maximum voltage of −90 V fine grains were detected due to the formation of numerous nuclei resulting from bombardment of high energy particles. The bias voltage had little effect on the bonding state of In, Sn and O ions.     

An Experimental Low-Cost, Low-Data-Rate Rapid Structural Assessment Network

In this paper, we present the design, implementation, and experimental evaluation of a wireless sensor network for real-time structural ldquohealthrdquo monitoring. We use simple custom-built gages to detect cracks in critical structural elements. The main data reports require no structural analysis for interpretation, have a low data rate, and are naturally resilient to loss. We show how a variety of low-cost, off-the-shelf data acquisition/communication devices can be used to support remote monitoring by a control center. The heterogeneous hardware is accommodated by the use of open technology standards and a software architecture that is portable, modular, and highly configurable. We present an experimental evaluation of our structural-assessment network done using a full-scale three-story reinforced concrete building that was tested under lateral forces emulating forces induced by earthquakes. Our results show that a set of 12 strategically positioned sensors achieved a 100% detection rate for cracks crossing sensors and a zero false-alarm rate (in the sense that all signals exceeding a preset threshold were traced to cracks exceeding a specified total width).     

How much do I tell thee? Strategies for managing information to parents among American adolescents from Chinese, Mexican, and European backgrounds.

Strategies for managing information about activities to parents, including partial disclosure, avoidance, lying, and full disclosure, were examined in 479 American adolescents (M = 16.38 years, SD = 0.77) varying in generational status and from Mexican, Chinese, and European backgrounds. Information management strategies for personal, prudential, and overlapping (multifaceted) activities as defined within social domain theory were examined. With age, parental education, and generational status controlled, Chinese American adolescents partially disclosed more to mothers about personal and multifaceted activities than did Mexican American adolescents and more to fathers about personal activities than did European American teens. In contrast, European and Mexican American adolescents fully disclosed more to mothers about personal activities than did Chinese-origin adolescents. Strategies varied by generation among Chinese American youth; second-generation adolescents avoided discussing activities with parents more than did immigrants. Adolescents who fully disclosed about all activities and lied less about multifaceted and personal activities reported stronger endorsement of obligations to assist their families, more trust in parents, and less problem behavior. More depressed mood was associated with more lying about personal activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of three‐dimensional virtual reality and traditional training methods on mental workload and training performance

Industries will implement effective training programs to improve training performance, and an ideal training performance occurs under proper mental workload (MWL). Virtual reality (VR) has recently been widely utilized in training; however, only a few studies have investigated its effects on MWL and training performance simultaneously. The purpose of this study is to investigate the effects of VR training and traditional training methods, such as technical manuals (TM) and multimedia films (MF), on training performance and MWL. The results of the performance measurement show that VR training is considered the best training method compared to TM and MF, particularly in the case of complex tasks. The results of physiological measurements (GSR [galvanic skin response], LF% [low frequency], and LF/HF [high frequency] ratio) show a significant difference between reading TM and using computer (MF and VR), wherein the latter has a lower MWL. However, no significant difference in subjective MWL assessment (NASA‐TLX [task load index]) and HF% measurement is found.