85°C investigation of uncooled 10-Gb/s directly modulatedInGaAsP RWG GC-DFB lasers

The 10-Gb/s directly modulated performance of InGaAsP ridge waveguide (RWG) gain coupled (GC) DFB lasers is investigated up to 85°C. At room temperature, devices have relaxation oscillation frequencies f_relax greater than 20 GHz and damping Γ greater than 100 GHz, f_relax is greater than 6 GHz at 85°C. Constant output power or extinction ratio are possible from 25°C to 75°C chip temperature, with open eyes observable up to 85°C. Back-to-back transmission measurements in a Nortel Networks OC-192 system show error free transmission of a 2²³-1 pseudorandom bit sequence at 83°C     

Instability Thresholds in General Nonlinear Ring Resonators

Abstract

By considering a passive ring cavity with linear absorption in the dispersive limit, a unified analysis is presented for tuning-optimized minimum instability thresholds; the treatment is general, allowing consideration of arbitrary material response times, cavity tuning and finesse. In the adiabatic limit (τ → 0) the results reduce to the usual Ikeda map. The case of long medium-response time (τ → ∞) is treated in some detail in the high-finesse limit; these conditions being of particular relevance to semiconductor laser amplifiers. It is found analytically that in the high-finesse limit, both optical bistability and self-pulsing instabilities should exhibit the same low-threshold behaviour. An analytical expression is derived for the ‘instability threshold curve’, A ² B against B for minimum A ², in the mapping limit.     

Levitation-jet synthesis of In-O nanoparticles with room-temperature ferromagnetic properties

Octahedral and roughly spherical In-In₂O₃ nanoparticles ranging in average particle size from 30 up to 300 nm were prepared by levitation-jet aerosol synthesis through condensation of metal indium vapor in helium gas flow with gaseous oxygen/air injection at ambient and reduced pressure. Scanning electron microscopy (SEM), X-ray diffraction (XRD), BET measurements, UV–vis, FT-IR, Raman, XPS, and vibrating-sample magnetometry (VSM) characterized the nanoparticles. Room-temperature ferromagnetism with maximum magnetization of up to 0.17 emu/g was recorded for the nanoparticles. The results indicate a predominant role of the actual microstructure on the nanoparticle properties. It is suggested that the observed ferromagnetic ordering may be related to intrinsic defects at the In/In₂O₃ interface structure of such a composite material. This suggestion is in good agreement with the results of optical and XPS experiments on the NPs.     

On-site energy management challenges and opportunities: a contractor's perspective

Although numerous policies encourage CO₂ and energy consumption reduction within the UK non-domestic sector, most measures are primarily focused towards reducing operational impacts, but largely overlook embodied impacts, particularly within the construction process. On-site construction refers to the energy consumed during the installation of materials up to project practical completion and represents the largest share of construction process CO₂ emissions. Contractors have a pivotal role to play in reducing CO₂ and energy consumption due to their significant involvement in project procurement and on-site construction. The key challenges and opportunities are investigated for delivering on-site energy management within UK non-domestic projects from a contractor's perspective. A case study is presented of a large UK principal contractor's on-site energy management practices, based on a wide geographical sample of non-domestic projects and operatives. Shortcomings are found within the contractor's current on-site energy management procedure across the three reporting levels (director, operations and project). Findings identified the lack of data authentication as a significant challenge, whereas capturing additional project variables to facilitate future benchmarking was deemed as a key opportunity for on-site energy management enhancement.

Bien que de nombreuses politiques encouragent une réduction du CO₂ et de la consommation d'énergie dans le secteur non résidentiel au Royaume-Uni, la plupart des mesures visent principalement à réduire les impacts opérationnels, mais négligent largement les impacts intrinsèques, en particulier dans le processus de construction. La construction sur chantier fait référence à l'énergie consommée de l'installation des matériaux jusqu'à la réalisation concrète du projet et représente la part la plus importante des émissions de CO₂ au cours du processus de construction. Les entrepreneurs ont un rôle crucial à jouer dans la réduction du CO₂ et de la consommation d'énergie du fait de leur importante implication dans la passation des marchés et dans la construction sur chantier. Les principales difficultés et opportunités sont examinées pour que soit assurée une bonne gestion de l'énergie sur les chantiers dans les projets non résidentiels britanniques du point de vue de l'entrepreneur. Est présentée une étude de cas portant sur les pratiques de gestion de l'énergie sur les chantiers d'un important maître d'?uvre britannique, sur la base d'un large échantillon géographique de projets non résidentiels et de modes opératoires. Il est constaté des insuffisances dans la procédure actuelle de gestion de l'énergie qui est utilisée sur les chantiers par les entrepreneurs sur l'ensemble des trois niveaux hiérarchiques (directeur, exploitation et projet). Les constatations ont identifié le manque d'authentification des données comme un défi important à relever, tandis que la saisie de variables supplémentaires des projets pour faciliter l'évaluation future des performances a été considérée comme une opportunité essentielle pour l'amélioration de la gestion de l'énergie sur les chantiers.

Mots clés: processus de construction, entrepreneurs, gestion de l'énergie, indicateurs de performance environnementale, non résidentiel, construction sur chantier     

Life-cycle assessment of a 100% solar fraction thermal supply to a European apartment building using water-based sensible heat storage

Providing 100% of a building's heating and hot water using a solar thermal system in a European climate has been shown to be both practically feasible and functionally successful for a new apartment building in Switzerland. The research conducted a life cycle assessment of the solar thermal system and compared the results with an air-source heat-pump, ground-source heat pump, natural gas furnace, oil furnace and a wood-pellet furnace. Using a range of lifetime scenarios it was found that the solar thermal system displays potentially significant advantages over all other systems in terms of reductions for purchased primary energy (from 84 to 93%) and reductions in GHG emissions (from 59 to 97%). However, due to the heavy industrial processes and the particular metals used in manufacturing, the solar thermal system was shown to have a higher demand for resources which, in relation to the natural gas system, can be by a factor of almost 38. Potential impacts on ecosystem quality were marginally worse than for the heat-pump and fossil fuel systems due to resource use impacts whilst potential human health impacts were similar to the heat pump systems but better than the fossil and biomass fuelled systems.     

Effects of titanium on transcriptional and post-transcriptional regulation of fibronectin in human fibroblasts

The effects of commercially pure titanium (Ti) on the regulation of fibronectin gene expression and synthesis were investigated in early-passage human gingival fibroblasts. The fibroblasts were cultured on 50 nm Ti-coated silicon wafers treated with radio-frequency glow discharge prior to use and on Falcon tissue culture plastic (TCP) dishes as a control. Northern hybridization analysis revealed that fibroblasts cultured on Ti reduced the fibronectin mRNA level by 58% at 16 h, but increased it by 2.6-fold at 90 h, although the cell numbers and house-keeping gene GAPD mRNA levels on these two surfaces were essentially the same. The amount of total RNA was slightly less on the Ti surface. While the total [35S]methionine incorporation was essentially unaltered, the amount of [35S]methionine-labeled fibronectin was significantly increased in cells cultured on a Ti surface in early cultures but decreased in the late cultures. The apparent discrepancy between the increased fibronectin mRNA levels and decreased translation could be explained by a 30% reduction in fibronectin mRNA half life in cells cultured on Ti. The distribution of fibronectin between the medium and the cell layer also was altered on Ti surfaces, with a approximately 100-fold increase of fibronectin assembled in extracellular matrix at 16 h, but a 36% reduction at 90 h. In contrast, the amount of fibronectin recovered in the medium was essentially unchanged. The total amount of protein assembled into the extracellular matrix by cells on Ti increased 2.1-fold at 16 h but decreased by 19% in 90-h cultures. These significant changes in fibronectin gene activity and gene product distribution by cells cultured on Ti surfaces demonstrate that the surface chemistry of biomaterials can selectively regulate the cellular behavior at the molecular level and, conversely, that molecular biological techniques provide sensitive indicators of the molecular biocompatibility of implant materials.     

Identifying trends in the use of domestic appliances from household electricity consumption measurements

Results are presented from a monitoring study of the electricity consumption of a sample of UK domestic buildings. Five-minutely average whole house power consumption was recorded for 72 dwellings at five sites over a 2-year monitoring period. The mean annual electricity consumption for the households increased significantly by 4.5% (t = 1.9; p < 0.05, one-tailed) from the first to the second year of monitoring. New techniques are developed which estimate the electricity consumption of different appliance groups, based on analysis of the five-minutely monitored data. The overall increase in electricity consumption is attributed to a 10.2% increase in the consumption of ‘standby’ appliances (such as televisions and consumer electronics) and a 4.7% increase in the consumption of ‘active’ appliance (such as lighting, kettles and electric showers). The consumption of different energy user groups (low, medium and high) is also investigated and low and high users are identified as contributing to the overall increase in consumption. The need for further investigation, such as quantitative and qualitative studies, to improve understanding in domestic electricity consumption is discussed.     

Nonlinear Optics

Abstract

Coherence tomo- and topography have great potential in the building of optical measuring tools for a lot of different technical and biological applications. One major limiting property of scanning coherence methods is their data acquisition time. In this paper we describe two methods for increasing the measuring speed; one for an analogue and one for a digital preprocessing sensor. In particular, we present a novel scanning device for an analogue 1-D sensor which enables measurements with a very fast vertical scanning rate to be made. A periodical change of the optical path difference of up to 3 mm and frequencies of 1200 Hz and more can be achieved by using a resonant scanner. We describe an optical fibre setup using this novel scanner in combination with a homemade low cost light source which is most appropriate for optical fibre coherence application.