Low-voltage surface-normal electroabsorption modulators.

Surface-normal electroabsorption modulators (SNEAMs) are appealing for short-reach communication systems because of their outstanding properties, such as ultrawide bandwidth and polarization-insensitive response; however, due to their small active volumes, large voltage swings are typically required to obtain the best performance. Here we propose and demonstrate a novel, to the best of our knowledge, design that dramatically reduces the voltage needed by SNEAMs and significantly increases their extinction ratio. By shrinking the multiple quantum well stack of SNEAMs to the minimum and by optimizing their reflectivity with dielectric coatings of suitable refractive index and thickness, we obtain modulators that require drive voltages of only 1-2Vpp. We show that these novel devices largely outperform conventional SNEAMs.

Power insensitive surface-normal electroabsorption modulators.

Surface-normal electroabsorption modulators (SNEAMs) have unique electro-optic modulation properties; however, their behavior and performance at high light intensity is affected by thermal nonlinearities that take place in the modulator active volume. Here we show a novel, to the best of our knowledge, approach to make SNEAMs insensitive to optical power without the use of power-hungry heaters or feedback control systems. By passively compensating for the thermo-optic dependence of the SNEAM resonant cavity, we obtain an eight-fold reduction in the wavelength shift of the SNEAM response at 4 dBm of input power. Furthermore, we show no appreciable degradation in the SNEAM eye diagram at 25 Gbit/s, when the input power is increased up to 2 dBm, which is about four times higher than in conventional SNEAMs.

PAM-4 transmission up to 160 Gb/s with surface-normal electro-absorption modulators.

We report multi-level modulation in polarization-independent surface-normal electro-absorption modulators (SNEAMs). Four-level pulse amplitude modulation (PAM-4) at a line rate of 44 Gb/s is demonstrated on a fully packaged SNEAM with a 30 µm active area diameter and a 14 GHz electro-optic bandwidth. High-capacity PAM-4 transmission at 112 and 160 Gb/s is demonstrated on an unpackaged SNEAM chip, with a 15 µm active area diameter and ultrawide electro-optic bandwidth (≫65GHz). Fiber transmission is investigated for direct detection link lengths up to 23 km at 44 Gb/s and 2 km at 112 and 160 Gb/s, the highest multi-level modulation rates achieved on a SNEAM.

Free-space coherent optical communication with orbital angular, momentum multiplexing/demultiplexing using a hybrid 3D photonic integrated circuit.

We demonstrate free-space space-division-multiplexing (SDM) with 15 orbital angular momentum (OAM) states using a three-dimensional (3D) photonic integrated circuit (PIC). The hybrid device consists of a silica planar lightwave circuit (PLC) coupled to a 3D waveguide circuit to multiplex/demultiplex OAM states. The low excess loss hybrid device is used in individual and two simultaneous OAM states multiplexing and demultiplexing link experiments with a 20 Gb/s, 1.67 b/s/Hz quadrature phase shift keyed (QPSK) signal, which shows error-free performance for 379,960 tested bits for all OAM states.

The health of UK military personnel who deployed to the 2003 Iraq war: a cohort study.

BACKGROUND: Concerns have been raised about the mental and physical health of UK military personnel who deployed to the 2003 war in Iraq and subsequent tours of duty in the country. METHODS: We compared health outcomes in a random sample of UK armed forces personnel who were deployed to the 2003 Iraq war with those in personnel who were not deployed. Participants completed a questionnaire covering the nature of the deployment and health outcomes, which included symptoms of post-traumatic stress disorder, common mental disorders, general wellbeing, alcohol consumption, physical symptoms, and fatigue. FINDINGS: The participation rate was 62.3% (n=4722) in the deployed sample, and 56.3% (n=5550) in the non-deployed sample. Differences in health outcomes between groups were slight. There was a modest increase in the number of individuals with multiple physical symptoms (odds ratio 1.33; 95% CI 1.15-1.54). No other differences between groups were noted. The effect of deployment was different for reservists compared with regulars. In regulars, only presence of multiple physical symptoms was weakly associated with deployment (1.32; 1.14-1.53), whereas for reservists deployment was associated with common mental disorders (2.47, 1.35-4.52) and fatigue (1.78; 1.09-2.91). There was no evidence that later deployments, which were associated with escalating insurgency and UK casualties, were associated with poorer mental health outcomes. INTERPRETATION: For regular personnel in the UK armed forces, deployment to the Iraq war has not, so far, been associated with significantly worse health outcomes, apart from a modest effect on multiple physical symptoms. There is evidence of a clinically and statistically significant effect on health in reservists.

Patterns of drinking in the UK Armed Forces.

AIMS: To examine patterns of drinking in the UK Armed Forces, how they vary according to gender and other demographics, and to make comparisons with the general population. DESIGN: Large cross-sectional postal questionnaire study (response rate 60%). SETTING: United Kingdom. PARTICIPANTS: A random representative sample of the regular UK Armed Forces who were in service in March 2003 (n = 8686; 7937 men, 749 women). Comparisons were made with the general population of Great Britain. MEASUREMENTS: Alcohol consumption was assessed using the Alcohol Use Disorders Identification Test (AUDIT). FINDINGS: Sixty-seven per cent of men and 49% of women in the UK Armed Forces had an AUDIT score of 8+ (defined as hazardous drinking), compared to 38% of men and 16% of women in the general population. In both sexes, for all ages, the military have a higher prevalence of hazardous drinking. Binge drinking was associated with being younger, being in the Army, being single, being a smoker and being white. Among military men, heavy drinking (AUDIT score 16+) was associated with holding a lower rank, being younger, being single, being in the Naval Service or Army, being deployed to Iraq, not having children, being a smoker, having a combat role and having a parent with a drink or drug problem. CONCLUSIONS: Excessive alcohol consumption is more common in the UK Armed Forces than in the general population. There are certain socio-demographic characteristics associated with heavy drinking within the military; for example, young age, being single and being a smoker, which may allow the targeting of preventive interventions.

Screening of benzodiazepines in thirty European rivers.

Pharmaceuticals as environmental contaminants have received a lot of interest over the past decade but, for several pharmaceuticals, relatively little is known about their occurrence in European surface waters. Benzodiazepines, a class of pharmaceuticals with anxiolytic properties, have received interest due to their behavioral modifying effect on exposed biota. In this study, our results show the presence of one or more benzodiazepine(s) in 86% of the analyzed surface water samples (n = 138) from 30 rivers, representing seven larger European catchments. Of the 13 benzodiazepines included in the study, we detected 9, which together showed median and mean concentrations (of the results above limit of quantification) of 5.4 and 9.6 ng L-1, respectively. Four benzodiazepines (oxazepam, temazepam, clobazam, and bromazepam) were the most commonly detected. In particular, oxazepam had the highest frequency of detection (85%) and a maximum concentration of 61 ng L-1. Temazepam and clobazam were found in 26% (maximum concentration of 39 ng L-1) and 14% (maximum concentration of 11 ng L-1) of the samples analyzed, respectively. Finally, bromazepam was found only in Germany and in 16 out of total 138 samples (12%), with a maximum concentration of 320 ng L-1. This study clearly shows that benzodiazepines are common micro-contaminants of the largest European river systems at ng L-1 levels. Although these concentrations are more than a magnitude lower than those reported to have effective effects on exposed biota, environmental effects cannot be excluded considering the possibility of additive and sub-lethal effects.

A first European scale multimedia fate modelling of BDE-209 from 1970 to 2020.

The European Variant Berkeley Trent (EVn-BETR) multimedia fugacity model is used to test the validity of previously derived emission estimates and predict environmental concentrations of the main decabromodiphenyl ether congener, BDE-209. The results are presented here and compared with measured environmental data from the literature. Future multimedia concentration trends are predicted using three emission scenarios (Low, Realistic and High) in the dynamic unsteady state mode covering the period 1970-2020. The spatial and temporal distributions of emissions are evaluated. It is predicted that BDE-209 atmospheric concentrations peaked in 2004 and will decline to negligible levels by 2025. Freshwater concentrations should have peaked in 2011, one year after the emissions peak with sediment concentrations peaking in 2013. Predicted atmospheric concentrations are in good agreement with measured data for the Realistic (best estimate of emissions) and High (worst case scenario) emission scenarios. The Low emission scenario consistently underestimates measured data. The German unilateral ban on the use of DecaBDE in the textile industry is simulated in an additional scenario, the effects of which are mainly observed within Germany with only a small effect on the surrounding areas. Overall, the EVn-BTER model predicts atmospheric concentrations reasonably well, within a factor of 5 and 1.2 for the Realistic and High emission scenarios respectively, providing partial validation for the original emission estimate. Total mean MEC:PEC shows the High emission scenario predicts the best fit between air, freshwater and sediment data. An alternative spatial distribution of emissions is tested, based on higher consumption in EBFRIP member states, resulting in improved agreement between MECs and PECs in comparison with the Uniform spatial distribution based on population density. Despite good agreement between modelled and measured point data, more long-term monitoring datasets are needed to compare predicted trends in concentration to determine the rate of change of POPs within the environment.

Comparing measured and modelled PFOS concentrations in a UK freshwater catchment and estimating emission rates.

The lifecycle, sources and fate of perfluorooctane sulfonate (PFOS) continue to generate scientific and political interest, particularly since PFOS was listed by the Stockholm Convention and largely restricted in Europe. It continues to be detected in aquatic environments, with only limited studies into the on-going sources. This paper explores PFOS emissions discharged by the general population into a small catchment comprising two rivers in the UK. A sampling campaign was undertaken to improve our understanding of population-derived PFOS sources from sewage treatment plants (STPs) and in rivers. A corresponding modelling exercise allowed an emission estimate of 13µg/day/per capita to be derived for the Aire and Calder rivers. PFOS emission was linked to STP discharges bylinear regression of measured and modelled concntrations (R(2)=0.49-0.85). The model was able to accurately estimate the spatial trends of PFOS in the rivers, while predicted concentrations were within a factor of three based on per capita emission values taken from the literature. Measured PFOS concentrations in rivers suggested that emissions from STPs are partially dependent on treatment type, where plants with secondary or tertiary treatment such as activated sludge processes emit less PFOS, possibly due to increased partitioning and retention. With refinements based on the type of treatment at each STP, predictions were further improved. The total PFOS mass discharged annually via rivers from the UK has been estimated to be between 215 and 310kg, based on the per capita emission range derived in this study.

Estimating European historical production, consumption and atmospheric emissions of decabromodiphenyl ether.

A European scale production, consumption and environmental emissions inventory is produced for decabromodiphenyl ether (DecaBDE) for the period 1970-2020. A dynamic substance flow analysis model of DecaBDE is developed and emission of the main congener, BDE-209, to environmental compartments is estimated. From 1970 to 2010, it is estimated that a total of 185,000-250,000 tonnes of DecaBDE was consumed in Europe. Consumption peaked in the late 1990s at approximately 9,000 tonnes/year and has declined by ~30% in 2010. Predicted BDE-209 atmospheric emissions peak in 2004 at 10 tonnes/year. The waste management phase of the BDE-209 life cycle is responsible for the majority of atmospheric emissions via volatilisation and particle bound emissions from landfills, whilst leakage from Sewerage systems is the major source of emissions to the hydrosphere. Use of sewage sludge from wastewater treatment works as an agricultural fertiliser is the most important pathway of BDE-209 to soil. Although DecaBDE consumption has declined in recent years, the stock in use for 2010 remains considerable (60,000 tonnes) and is likely to act as a source of atmospheric emissions for several decades. Uncertainties exist in these estimations and more field or experimental data is needed to clarify the significance of certain emission pathways, in particular, emissions from landfill sites.

Atmospheric polybrominated diphenyl ethers (PBDEs) in the United Kingdom.

The occurrence of PBDEs has been studied in the atmosphere of four sites in the United Kingdom over a period of ten years. The concentrations have exhibited a sharp decrease after 2001-2003. This is evident in the urban sites of Manchester and London and at the semi-rural site of Hazelrigg. The average ΣPBDE half-lives for these three sites were 3.4, 2.0 and 3.5 years respectively. ΣPBDEs concentrations in the UK (in 2010 ΣPBDEs < 10 pg m(-3)) are among the lowest reported in literature. Comparison of concentrations to estimated emissions and employment of PBDE profiles suggest that PBDEs in the UK atmosphere originate from primary emissions from products that contain mainly the penta-BDE technical mixture. The detection of BDE-183 in the majority of samples hints that octa-bromodiphenylether has also been used extensively in the UK, however to a smaller extent than the penta- product.

Does psychoeducation help prevent post traumatic psychological distress?

Psychoeducation is increasingly used following trauma. The term covers the provision of information about the nature of stress, posttraumatic and other symptoms, and what to do about them. The provision of psychoeducation can also occur before possible exposure to stressful situations or, alternatively, after exposure. The intention of both is to ameliorate or mitigate the effects of exposure to extreme situations. Educational information can be imparted in a number of ways and can also form part of what has been termed psychological first aid. Despite its ubiquity, however, good evidence as to the value of psychoeducation is rare. Perhaps it could be assumed that psychoeducation, like education in general, is so obviously a "good thing" that it requires no evidence. In this paper we question the assumption, arguing that like any other intervention, psychoeducation needs to be backed up by empirical evidence. We will first present the case for and then the case against psychoeducation before reaching some conclusions and making some recommendations.

Mental health consequences of overstretch in the UK armed forces: first phase of a cohort study.

OBJECTIVE: To assess the relation between frequency and duration of deployment of UK armed forces personnel on mental health. DESIGN: First phase of a cohort study. SETTING: UK armed forces personnel. PARTICIPANTS: Operational history in past three years of a randomly chosen stratified sample of 5547 regulars with experience of deployment. MAIN OUTCOME MEASURES: Psychological distress (general health questionnaire-12), caseness for post-traumatic stress disorder, physical symptoms, and alcohol use (alcohol use disorders identification test). RESULTS: Personnel who were deployed for 13 months or more in the past three years were more likely to fulfil the criteria for post-traumatic stress disorder (odds ratio 1.55, 95% confidence interval 1.07 to 2.32), show caseness on the general health questionnaire (1.35, 1.10 to 1.63), and have multiple physical symptoms (1.49, 1.19 to 1.87). A significant association was found between duration of deployment and severe alcohol problems. Exposure to combat partly accounted for these associations. The associations between number of deployments in the past three years and mental disorders were less consistent than those related to duration of deployment. Post-traumatic stress disorder was also associated with a mismatch between expectations about the duration of deployment and the reality. CONCLUSIONS: A clear and explicit policy on the duration of each deployment of armed forces personnel may reduce the risk of post-traumatic stress disorder. An association was found between deployment for more than a year in the past three years and mental health that might be explained by exposure to combat.