Superluminal tunnelling times as weak values

Abstract

We consider the tunnelling particle as a pre- and post-selected system and prove that the tunnelling time is the expectation value of the position of a ‘clock’ degree of freedom weakly coupled to it. Such a value, called a ‘weak value’, typically falls outside the eigenvalue spectrum of the operator. The appearance of unusual weak values has been associated with a unique interference structure called ‘superoscillations’ (band-limited functions which on a finite interval, approximate functions with spectra well outside their band). It is proposed that superoscillations play an important role in the interferences which give rise to superluminal effects. To demonstrate that, we consider a certain simple tunnelling barrier which allows a wave packet to travel in zero time and negligible distortion, a distance arbitrarily longer than the width of the wave packet. The peak is shown to result from a superoscillatory superposition at the tail. Similar reasoning applies to the dwell time. For this system, both the Wigner time (related to the group velocity) and a clock time correspond to superluminal velocities.     

Parameter Sweep Workflows for Modelling Carbohydrate Recognition

Carbohydrate recognition is a phenomenon critical to a number of biological functions in humans. Understanding the dynamic behaviour of oligosaccharides should help in the discovery of the mechanisms which lead to specific and selective recognition of carbohydrates by proteins. Computer programs which can provide insight into such biological recognition processes have significant potential to contribute to biomedical research if the results of the simulation can prove consistent with the outcome of conventional wet laboratory experiments. In order to validate these simulation tools and support their wider uptake by the bio-scientist research community, high-level easy to use integrated environments are required to run massively parallel simulation workflows. This paper describes how the ProSim Science Gateway, based on the WS-PGRADE Grid portal, has been created to execute and visualise the results of complex parameter sweep workflows for modelling carbohydrate recognition.     

What role for microgeneration in a shift to a low carbon domestic energy sector in the UK?

Domestic energy use accounts for more than a quarter of CO₂ emissions in the UK. Traditional approaches to energy reduction look at direct emissions savings, and recommend insulation and efficiency as more cost-effective than microgeneration. However, microgeneration has indirect, ‘soft’ benefits and could play a significant role in emissions reduction. Current uptake of microgeneration in the UK is low, with various barriers—economic, technical, cultural, behavioural and institutional—both to uptake and to maximising energy and emissions savings once installed. Subsidies and spreading information alone do not guarantee maximising uptake, and even if successful, this is not enough to maximise savings. The industry focuses on maximising sales, with no incentives to ensure best installations and use; householders do not have access to the best information, and user behaviour does not maximise energy and emission savings. This is related to a broader state of socio-technical ‘lock-in’ in domestic energy use; there’s a lack of connection between personal behaviour and energy consumption, let alone global climate change. This suggests that a major cultural–behavioural shift is needed to reduce energy/emissions in the home. Transition theory and strategic niche management provide insights into possible systemic change and a suitable framework for future policies, such as supporting a variety of radically innovative niches, both technological and social. Microgeneration, properly employed, has the potential to play a part in such a transition by increasing awareness and energy literacy and empowering people to seriously engage in energy debates as producers, as well as consumers, of energy. This deeper understanding and heightened responsibility are crucial in a shift toward bottom-up emission-reducing behaviour change and better acceptance of top-down energy-saving policy measures, as part of a new domestic energy paradigm. The implications for policy are that, as well as supporting the technologies, it needs to support existing niches and to develop new niche experiments. Policy needs to consider how to promote empowerment and responsibility and support or even develop new energy sector models; this will involve a range of stakeholders and multiple governance levels, not just national incentive schemes.     

An Overview of Synergistic Data Tools for Biological Scrutiny

A network of biological databases is reviewed, supplying a framework for studies of human genes and the association of their genomic variations with human phenotypes. The network is composed of GeneCards, the human gene compendium, which provides comprehensive information on all known and predicted human genes, along with its suite members GeneDecks and GeneLoc. Two databases are shown that address genes and variations focusing on olfactory reception (HORDE) and transduction (GOSdb). In the realm of disease scrutiny, we portray MalaCards, a novel comprehensive database of human diseases and their annotations. Also shown is GeneKid, a tool aimed at generating novel kidney disease biomarkers using systems biology, as well as Xome, a database for whole-exome next-generation DNA sequences for human diseases in the Israeli population. Finally, we show LifeMap Discovery, a database of embryonic development, stem cell research and regenerative medicine, which links to both GeneCards and MalaCards.     

Whodunnit – Searching for the most important feature types signalling emotion-related user states in speech

In this article, we describe and interpret a set of acoustic and linguistic features that characterise emotional/emotion-related user states – confined to the one database processed: four classes in a German corpus of children interacting with a pet robot. To this end, we collected a very large feature vector consisting of more than 4000 features extracted at different sites. We performed extensive feature selection (Sequential Forward Floating Search) for seven acoustic and four linguistic types of features, ending up in a small number of ‘most important’ features which we try to interpret by discussing the impact of different feature and extraction types. We establish different measures of impact and discuss the mutual influence of acoustics and linguistics.     

Iterative Power Pricing for Distributed Spectrum Coordination in DSL

In this letter we propose a novel distributed technique for dynamic spectrum management of DSL lines. The proposed method generalizes several known techniques, by imposing pricing for use of spectrum. We propose a simple mechanism that allows each line to choose an appropriate pricing function independently of the other lines. Finally, by incorporating a total power constraint, the algorithm is capable of self-correcting an overly ambitious pricing function. We also provide simulated examples based on measured DSL lines.     

COOLCEP (cool clean efficient power): A novel CO2-capturing oxy-fuel power system with LNG (liquefied natural gas) coldness energy utilization

A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO₂ and other emissions and a high efficiency. The plant operates as a subcritical CO₂ Rankine-like cycle. Beside the power generation, the system provides refrigeration in the CO₂ subcritical evaporation process, thus it is a cogeneration system with two valued products. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO₂ can be withdrawn from the cycle without consuming additional power. Two system variants are analyzed and compared, COOLCEP-S and COOLCEP-C. In the COOLCEP-S cycle configuration, the working fluid in the main turbine expands only to the CO₂ condensation pressure; in the COOLCEP-C cycle configuration, the turbine working fluid expands to a much lower pressure (near-ambient) to produce more power. The effects of some key parameters, the turbine inlet temperature and the backpressure, on the systems' performance are investigated. It was found that at the turbine inlet temperature of 900 °C, the energy efficiency of the COOLCEP-S system reaches 59%, which is higher than the 52% of the COOLCEP-C one. The capital investment cost of the economically optimized plant is estimated to be about 750 EUR/kWe and the payback period is about 8–9 years including the construction period, and the cost of electricity is estimated to be 0.031–0.034 EUR/kWh.     

Sustainable energy development: The present (2009) situation and possible paths to the future

Recent estimates and forecasts of the oil, gas, coal resources and their reserve/production ratio, nuclear and renewable energy potential, and energy uses are surveyed. A brief discussion of the status, sustainability (economic, environmental and social impact), and prospects of fossil, nuclear and renewable energy use, and of power generation (including hydrogen, fuel cells, micropower systems, and the futuristic concept of generating power in space for terrestrial use), is presented. Comments about energy use in general, with more detailed focus on insufficiently considered areas of transportation and buildings are brought up. Ways to resolve the problem of the availability, cost, and sustainability of energy resources alongside the rapidly rising demand are discussed. The author’s view of the promising energy R&D areas, their potential, foreseen improvements and their time scale, and last year’s trends in government funding are presented.     

Synthesis,structure and stability of fac-[FeII(CO)3X3]1− (X = Br,I)

fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are synthesized and their structures have been determined. They are the first crystallographically characterized iron tricarbonyl trihalide complexes. fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are fairly thermally stable and therefore lead themselves as excellent starting materials for the preparation of various iron carbonyl complexes since both the halide and carbonyl ligands are substitutionally labile.