Dichotomous feedback: a signal sequestration-based feedback mechanism for biocontroller design

We introduce a new design framework for implementing negative feedback regulation in synthetic biology, which we term ‘dichotomous feedback’. Our approach is different from current methods, in that it sequesters existing fluxes in the process to be controlled, and in this way takes advantage of the process’s architecture to design the control law. This signal sequestration mechanism appears in many natural biological systems and can potentially be easier to realize than ‘molecular sequestration’ and other comparison motifs that are nowadays common in biomolecular feedback control design. The loop is closed by linking the strength of signal sequestration to the process output. Our feedback regulation mechanism is motivated by two-component signalling systems, where a second response regulator could be competing with the natural response regulator thus sequestering kinase activity. Here, dichotomous feedback is established by increasing the concentration of the second response regulator as the level of the output of the natural process increases. Extensive analysis demonstrates how this type of feedback shapes the signal response, attenuates intrinsic noise while increasing robustness and reducing crosstalk.     

Exploring barriers and opportunities in adopting crowdsourcing based new product development in manufacturing SMEs

Crowdsourcing is an innovative business practice of obtaining needed services, ideas, or content or even funds by soliciting contributions from a large group of people(the ‘Crowd'). The potential benefits of utilizing crowdsourcing in product design are well-documented, but little research exists on what are the barriers and opportunities in adopting crowdsourcing in new product development(NPD) of manufacturing SMEs. In order to answer the above questions, a Proof of Market study is carried out on crowdsourcing-based product design under an Innovate UK funded Smart project, which aims at identifying the needs, challenges and future development opportunities associated with adopting crowdsourcing strategies for NPD. The research findings from this study are reported here and can be used to guide future development of crowdsourcing-based collaborative design methods and tools and provide some practical references for industry to adopt this new and emerging collaborative design method in their business.     

Ultrafast Dynamics of Localized and Delocalized Polaron Transitions in P3HT/PCBM Blend Materials: The Effects of PCBM Concentration

Nowadays, organic solar cells have the interest of engineers for manufacturing flexible and low cost devices. The considerable progress of this nanotechnology area presents the possibility of investigating new effects from a fundamental science point of view. In this letter we highlight the influence of the concentration of fullerene molecules on the ultrafast transport properties of charged electrons and polarons in P3HT/PCBM blended materials which are crucial for the development of organic solar cells. Especially, we report on the femtosecond dynamics of localized (P₂ at 1.45 eV) and delocalized (DP₂ at 1.76 eV) polaron states of P3HT matrix with the addition of fullerene molecules as well as the free-electron relaxation dynamics of PCBM-related states. Our study shows that as PCBM concentration increases, the amplified exciton dissociation at bulk heterojunctions leads to increased polaron lifetimes. However, the increase in PCBM concentration can be directly related to the localization of polarons, creating thus two competing trends within the material. Our methodology shows that the effect of changes in structure and/or composition can be monitored at the fundamental level toward optimization of device efficiency.     

CO2 emissions,GDP and energy intensity: A multivariate cointegration and causality analysis for Greece, 1977–2007

This paper deals with the causal relationship analysis between Gross Domestic Product, Energy Intensity and CO₂ emissions in Greece from 1977 to 2007, by means of Johansen cointegration tests and Granger-causality tests based on a multivariate Vector Error Correction Modeling. Results indicate that there is a set of uni-directional and bi-directional causalities among the selected time series. We performed a model Variance Decomposition Analysis using Choleski technique and we provided a comparison with other studies. The findings of the study have significant policy implications for countries like Greece as the decoupling of CO₂ emissions and economic growth seems quite unlikely.     

Renewable energy sources (RES) projects and their barriers on a regional scale: The case study of wind parks in the Dodecanese islands, Greece

The increasing energy challenges faced, in particular, by isolated communities, such as insular communities, call for an integrated, flexible and easy-to-apply methodology aiming at providing a list of renewable energy sources) (RES) projects capable to reduce green house gas (GHG) emissions, satisfy future energy forecasts and reach the objectives of international/national energy directives and obligations, as, for example, the ones set by the Kyoto Protocol by 2010. The EU project EMERGENCE 2010 developed such a methodology that is implemented here in the case study of wind parks in the Dodecanese islands in Greece. The results obtained consist of a final list of financially viable RES wind projects, for which various barriers have been previously identified and assessed. The additional advantages of the proposed methodology is that besides providing as an end result a comprehensive list of RES projects adopted to specific criteria and regional priorities, it also allows space for involving – from early stages – the local community and stakeholders in the decision-making process (participatory planning); in this way, the EMERGENCE 2010 methodology may assist towards the RES promotion and public acceptance, the profitability of RES investments and the regional sustainable development.     

Monitoring Charge Exchange in P3HT-Nanotube Composites Using Optical and Electrical Characterisation

Charge exchange at the bulk heterojunctions of composites made by mixing single wall nanotubes (SWNTs) and polymers show potential for use in optoelectronic devices such as solar cells and optical sensors. The density/total area of these heterojunctions is expected to increase with increasing SWNT concentration but the efficiency of solar cell peaks at low SWNT concentrations. Most researchers use current–voltage measurements to determine the evolution of the SWNT percolation network and optical absorption measurements to monitor the spectral response of the composites. However, these methods do not provide a detailed account of carrier transport at the concentrations of interest; i.e., near or below the percolation threshold. In this article, we show that capacitance–voltage (C–V) response of (metal)-(oxide)-(semiconducting composite) devices can be used to fill this gap in studying bulk heterojunctions. In an approach where we combine optical absorption methods with C–V measurements we can acquire a unified optoelectronic response from P3HT-SWNT composites. This methodology can become an important tool for optoelectronic device optimization.     

Surface-Related States in Oxidized Silicon Nanocrystals Enhance Carrier Relaxation and Inhibit Auger Recombination

We have studied ultrafast carrier dynamics in oxidized silicon nanocrystals (NCs) and the role that surface-related states play in the various relaxation mechanisms over a broad range of photon excitation energy corresponding to energy levels below and above the direct bandgap of the formed NCs. Transient photoinduced absorption techniques have been employed to investigate the effects of surface-related states on the relaxation dynamics of photogenerated carriers in 2.8 nm oxidized silicon NCs. Independent of the excitation photon energy, non-degenerate measurements reveal several distinct relaxation regions corresponding to relaxation of photoexcited carriers from the initial excited states, the lowest indirect states and the surface-related states. Furthermore, degenerate and non-degenerate measurements at difference excitation fluences reveal a linear dependence of the maximum of the photoinduced absorption (PA) signal and an identical decay, suggesting that Auger recombination does not play a significant role in these nanostructures even for fluence generating up to 20 carriers/NC.     

Couette flow through a porous medium of a high prandtl number fluid with temperature-dependent viscosity

The velocity and temperature profiles for an impulsively started Couette flow have been derived for a fluid with a high and strongly temperature-dependent viscosity when the flow takes place through a porous medium. The steady as well as the transient state flows are discussed and the influence of the medium permeability is assessed. In the steady state the presence of the porous medium causes higher maximum temperatures only for sufficiently low permeabilities and in all cases significantly lower velocity profiles. The flow development times tend to be higher for the low permeabilities only for high Nahme numbers. For the transient state it is noticeable that, in all cases, the velocity develops much more rapidly than the temperature and that the presence of the porous medium accelerates this tendency. Finally the medium permeability produces skew temperature profiles and higher temperature time gradients at all times.     

Numerical investigation of the oxy-fuel combustion in large scale boilers adopting the ECO-Scrub technology

The present paper presents a three-dimensional numerical investigation of a pulverized-fuel, tangentially-fired utility boiler located at Florina/Greece under air, partial and full oxy-fuel conditions. Heat and mass transfer and major species concentration, such as CO₂, CO and O₂ are calculated; whilst the results for the reference air case scenario studied are in good agreement with the corresponding operational data measured in the plant, both for combustion calculations and NO_x emissions. Results for the partial and full oxy-fuel operation scenarios are in line with similar experimental and numerical investigations found in the recent literature. This numerical investigation of oxy-fuel conditions scenarios prior to their implementation under real scale conditions demonstrates the utmost of its importance, since significant results regarding the operation of a boiler in terms of lignite particle trajectories and burning rates are attained. Furthermore, NO_x calculations have been performed for all the examined case studies.     

Smoking prevention: implications of study design, research setting, and goals.

Collaborations among various disciplines concerned with smoking prevention are gaining in currency. Such collaborations are predicated, in part, on recognizing both the implicit assumptions in different fields and the consequences of these assumptions. These issues, however, are often ignored in transdisciplinary research. In this article, we demonstrate how simple indices, such as the risk ratio, attributable fraction, or R(2), may have different implications for causal inference and interventions, depending on study setting and research goals.