Non-periodic quasi-stable nonlinear optical carrier pulses with sliding chirp-free points for transmission at 40 Gbit/s rate

In this paper, we demonstrate the possibility of reaching a quasi-stable nonlinear transmission regime with carrier pulses of 12.5 ps width in multi-channel 40 Gbit/s systems. The quasi-stable pulses that are presented in this work for the first time are not dispersion-managed solitons, and are indeed supported by a large normal span average dispersion and misbalanced optical amplification, and representing a new type of nonlinear carrier.

A catalytic reactor for the trapping of free radicals from gas phase oxidation reactions

A catalytic reactor for the trapping of free radicals originating from gas phase catalytic reactions is described and discussed. Radical trapping and identification were initially carried out using a known radical generator such as dicumyl peroxide. The trapping of radicals was further demonstrated by investigating genuine radical oxidation processes, e.g., benzaldehyde oxidation over manganese and cobalt salts. The efficiency of the reactor was finally proven by the partial oxidation of cyclohexane over MoO3, Cr2O3, and WO3, which allowed the identification of all the radical intermediates responsible for the formation of the products cyclohexanol and cyclohexanone. Assignment of the trapped radicals was carried out using spin trapping technique and X -band electron paramagnetic resonance spectroscopy. © 2010 American Institute of Physics.

The governance of online expression in a networked world:free-speech, surveillance and censorship

In recent years, we have witnessed the mushrooming of pro- democracy and protest movements not only in the Arab world, but also within Europe and the Americas. Such movements have ranged from popular upheavals, like in Tunisia and Egypt, to the organization of large- scale demonstrations against unpopular policies, as in Spain, Greece and Poland. What connects these different events are not only their democratic aspirations, but also their innovative forms of communication and organization through online means, which are sometimes considered to be outside of the State’s control. At the same time, however, it has become more and more apparent that countries are attempting to increase their understanding of, and control over, their citizens’ actions in the digital sphere. This involves striving to develop surveillance instruments, control mechanisms and processes engineered to dominate the digital public sphere, which necessitates the assistance and support of private actors such as Internet intermediaries. Examples include the growing use of Internet surveillance technology with which online data traffic is analysed, and the extensive monitoring of social networks. Despite increased media attention, academic debate on the ambivalence of these technologies, mechanisms and techniques remains relatively limited, as is discussion of the involvement of corporate actors. The purpose of this edited volume is to reflect on how Internet-related technologies, mechanisms and techniques may be used as a means to enable expression, but also to restrict speech, manipulate public debate and govern global populaces.

In situ growth strategy for highly efficient Ag2CO3/g-C3N4 hetero/nanojunctions with enhanced photocatalytic activity under sunlight irradiation

Developing novel heterojunction photocatalysts is a powerful strategy for improving the separation efficiency of photogenerated charge carriers, which is attracting the intense research interest in photocatalysis. Herein we report a highly efficient hetero/nanojunction consisting of Ag2CO3 nanoparticles grown on layered g-C3N4 nanosheets synthesized via a facile and template free in situ precipitation method. The UV–vis diffuse reflectance studies revealed that the synthesized Ag2CO3/g-C3N4 hetero/nanojunctions exhibit a broader and stronger light absorption in the visible light region, which is highly beneficial for absorbing the visible light in the solar spectrum. The optimum photocatalytic activity of Ag2CO3/g-C3N4 at a weight content of 10% Ag2CO3 for the degradation of Rhodamine B was almost 5.5 and 4 times as high as that of the pure Ag2CO3 and g-C3N4, respectively. The enhanced photocatalytic activity of the Ag2CO3/g-C3N4 hetero/nanojunctions is due to synergistic effects including the strong visible light absorption, large specific surface area, and high charge transfer and separation efficiency. More importantly, the high photostability and low use of the noble metal silver which reduces the cost of the material. Therefore, the synthesized Ag2CO3/g-C3N4 hetero/nanojunction photocatalyst is a promising candidate for energy storage and environment protection applications.

Surface plasmon resonance-induced photocatalysis by Au nanoparticles decorated mesoporous g-C3N4 nanosheets under direct sunlight irradiation

In recent years, surface plasmon-induced photocatalytic materials with tunable mesoporous framework have attracted considerable attention in energy conversion and environmental remediation. Herein we report a novel Au nanoparticles decorated mesoporous graphitic carbon nitride (Au/mp-g-C3N4) nanosheets via a template-free and green in situ photo-reduction method. The synthesized Au/mp-g-C3N4 nanosheets exhibit a strong absorption edge in visible and near-IR region owing to the surface plasmon resonance effect of Au nanoparticles. More attractively, Au/mp-g-C3N4 exhibited much higher photocatalytic activity than that of pure mesoporous and bulk g-C3N4 for the degradation of rhodamine B under sunlight irradiation. Furthermore, the photocurrent and photoluminescence studies demonstrated that the deposition of Au nanoparticles on the surface of mesoporous g-C3N4 could effectively inhibit the recombination of photogenerated charge carriers leading to the enhanced photocatalytic activity. More importantly, the synthesized Au/mp-g-C3N4 nanosheets possess high reusability. Hence, Au/mp-g-C3N4 could be promising photoactive material for energy and environmental applications.

Developing actions to minimise avoidable waste and its challenge to plant safety

Purpose: Considering the UK's limited capacity for waste disposal (particularly for hazardous/radiological waste) there is growing focus on waste avoidance and minimisation to lower the volumes of waste being sent to disposal. The hazardous nature of some waste can complicate its management and reduction. To address this problem there was a need for a decision making methodology to support managers in the nuclear industry as they identify ways to reduce the production of avoidable hazardous waste. The methodology we developed is called Waste And Sourcematter Analysis (WASAN). A methodology that begins the thought process at the pre-waste creation stage (i.e. Avoid). Design/methodology/ approach: The methodology analyses the source of waste, the production of waste inside the facility, the knock on effects from up/downstream facilities on waste production, and the down-selection of waste minimisation actions/options. WASAN has been applied to case studies with licencees and this paper reports on one such case study - the management of plastic bags in Enriched Uranium Residues Recovery Plant (EURRP) at Springfields (UK) where it was used to analyse the generation of radioactive plastic bag waste. Findings: Plastic bags are used in EURRP as a strategy to contain hazard. Double bagging of materials led to the proliferation of these bags as a waste. The paper reports on the philosophy behind WASAN, the application of the methodology to this problem, the results, and views from managers in EURRP. Originality/value: This paper presents WASAN as a novel methodology for analyzing the minimization of avoidable hazardous waste. This addresses an issue that is important to many industries e.g. where legislation enforces waste minimization, where waste disposal costs encourage waste avoidance, or where plant design can reduce waste. The paper forms part of the HSE Nuclear Installations Inspectorate's desire to work towards greater openness and transparency in its work and the development in its thinking.© Crown Copyright 2011.

Synthesis of a novel and stable g-C3N4–Ag3PO4 hybrid nanocomposite photocatalyst and study of the photocatalytic activity under visible light irradiation

A facile and reproducible template free in situ precipitation method has been developed for the synthesis of Ag3PO4 nanoparticles on the surface of a g-C3N4 photocatalyst at room temperature. The g-C3N4–Ag3PO4 organic–inorganic hybrid nanocomposite photocatalysts were characterized by various techniques. TEM results show the in situ growth of finely distributed Ag3PO4 nanoparticles on the surface of the g-C3N4 sheet. The optimum photocatalytic activity of g-C3N4–Ag3PO4 at 25 wt% of g-C3N4 under visible light is almost 5 and 3.5 times higher than pure g-C3N4 and Ag3PO4 respectively. More attractively, the stability of Ag3PO4 was improved due to the in situ deposition of Ag3PO4 nanoparticles on the surface of the g-C3N4 sheet. The improved performance of the g-C3N4–Ag3PO4 hybrid nanocomposite photocatalysts under visible light irradiation was induced by a synergistic effect, including high charge separation efficiency of the photoinduced electron–hole pair, the smaller particle size, relatively high surface area and the energy band structure. Interestingly, the heterostructured g-C3N4–Ag3PO4 nanocomposite significantly reduces the use of the noble metal silver, thereby effectively reducing the cost of the Ag3PO4 based photocatalyst.

Synthesis of magnetically separable and recyclable g‑C3N4−Fe3O4 hybrid nanocomposites with enhanced photocatalytic performance under visible-light irradiation

Herein we demonstrate a facile, reproducible, and template-free strategy to prepare g-C3N4–Fe3O4 nanocomposites by an in situ growth mechanism. The results indicate that monodisperse Fe3O4 nanoparticles with diameters as small as 8 nm are uniformly deposited on g-C3N4 sheets, and as a result, aggregation of the Fe3O4 nanoparticles is effectively prevented. The as-prepared g-C3N4–Fe3O4 nanocomposites exhibit significantly enhanced photocatalytic activity for the degradation of rhodamine B under visible-light irradiation. Interestingly, the g-C3N4–Fe3O4 nanocomposites showed good recyclability without loss of apparent photocatalytic activity even after six cycles, and more importantly, g-C3N4–Fe3O4 could be recovered magnetically. The high performance of the g-C3N4–Fe3O4 photocatalysts is due to a synergistic effect including the large surface-exposure area, high visible-light-absorption efficiency, and enhanced charge-separation properties. In addition, the superparamagnetic behavior of the as-prepared g-C3N4–Fe3O4 nanocomposites also makes them promising candidates for applications in the fields of lithium storage capacity and bionanotechnology.