Electrical transport through a single nanoscale semiconductor branch point

Semiconductor tetrapods are three-dimensional (3D) branched nanostructures, representing a new class of materials for electrical conduction. We employ the single-electron transistor approach to investigate how charge carriers migrate through single nanoscale branch points of tetrapods. We find that carriers can delocalize across the branches or localize and hop between arms depending on their coupling strength. In addition, we demonstrate a new single-electron transistor operation scheme enabled by the multiple branched arms of a tetrapod: one arm can be used as a sensitive arm-gate to control the electrical transport through the whole system.     

Tunable double quantum dots in InAs nanowires defined by local gate electrodes

We report on low-temperature transport measurements on single and double quantum dots defined using local gates to electrostatically deplete InAs nanowires grown by chemical beam epitaxy. This technique allows us to define multiple quantum dots along a semiconducting nanowire and tune the coupling between them.     

An integrated analysis of ergonomics and time consumption in Swedish 'craft-type' car disassembly

Car disassembly is at the edge of extensive rationalization due to increased legislative demands for recycling. This study focused on (1) assessing current mechanical exposures (physical work loads) for comparison with future rationalised systems, with particular emphasis on time aspects, (2) analysing disassembly work in terms of time consumption and exposures in constituent tasks as defined by a loss analysis technique, and (3) predicting the consequences of car disassembly rationalisation for mechanical exposures. The study showed that disassembly implied pronounced circulatory loads, and that more walking and higher lumbar peak loads were found than in studies of assembly work. Value-adding tasks comprised 30% of the total working time, and implied higher postural exposures for the head, arm, trunk and wrist, as well as less opportunities to recover, as compared to non-value-adding tasks. Organisational-type rationalization can be expected to increase the time spent in value-adding work, thus increasing local exposures for the average worker, while a concurrent increase in mechanization level might reduce circulatory exposures, the amount of walking, and peak lumbar loads.     

Multivalent HSA conjugates of 3'-sialyllactose are potent inhibitors of adenoviral cell attachment and infection

Adenoviruses of serotypes 8, 19 and 37 are the major cause of the severe eye infection EKC (epidemic keratoconjunctivitis). In general, all adenoviruses interact with their cellular receptors through the fibre proteins, which extend from the virus particle. Recently, adenovirus type 37 (Ad37) was found to bind and infect human corneal cells through attachment to carbohydrate structures that carry terminal alpha-(2-3)-linked sialic acids. Herein we present a synthetic route to a 3'-sialyllactose derivative and corresponding multivalent HSA conjugates with varying orders of valency. The potential of these compounds as inhibitors of EKC-causing adenovirus of serotype Ad37, was studied with both a binding assay and an infectivity assay. The results revealed that these compounds effectively prevent Ad37 from binding to and infecting human corneal epithelial (HCE) cells. Moreover, the inhibition is significantly increased with higher orders of multivalency.     

Distributed cross-layer coordination of congestion control and resource allocation in S-TDMA wireless networks

We consider the problem of joint congestion control and resource allocation in spatial-TDMA wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve both transmission scheduling and power allocation. Starting from the performance limitations of a centralized optimization based on global network information, we proceed systematically in our development of two distributed and transparent protocols that rely on local information only. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem, and demonstrate how it suggests a distributed solution based on TCP/AQM and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed link scheduling and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.

The Peak of the Oil Age – Analyzing the world oil production Reference Scenario in World Energy Outlook 2008

The assessment of future global oil production presented in the IEA’s World Energy Outlook 2008 (WEO 2008) is divided into 6 fractions; four relate to crude oil, one to non-conventional oil, and the final fraction is natural-gas-liquids (NGL). Using the production parameter, depletion-rate-of-recoverable-resources, we have analyzed the four crude oil fractions and found that the 75 Mb/d of crude oil production forecast for year 2030 appears significantly overstated, and is more likely to be in the region of 55 Mb/d. Moreover, analysis of the other fractions strongly suggests lower than expected production levels. In total, our analysis points to a world oil supply in 2030 of 75 Mb/d, some 26 Mb/d lower than the IEA predicts.     

A Danish case: portfolio evaluation and its impact on energy efficiency policy

A political agreement from 2005 stated that an evaluation of the entire Danish energy efficiency policy portfolio must be carried out before the end of 2008, with the aim to assess the following: (1) Is the policy portfolio sufficient to meet the energy efficiency targets? (2) Do the policies enable the national goals to be met in a cost-effective manner? (3) Is the overall design of the policy portfolio appropriate? The evaluation gave recommendations on how to improve and develop the portfolio, mainly using cost-effectiveness as criteria. The evaluation was completed in December 2008, and this paper presents the main findings and the subsequent impact on Danish policy. A key lesson learned is the importance of including all energy efficiency policies in the evaluation. Examining the entire portfolio of policies (as opposed to only selected policies) gave way to findings that would otherwise not have been captured. With its broad perspective, the evaluation found that the policy instruments prioritised the commercial and industrial sectors less than the household and public sectors. The recommendations made by the authors contributed to the implementation of new taxes for the commercial and industrial sectors together with the reform of the Electricity Saving Trust to a Centre for Energy Savings charged with energy savings within all sectors, except transport—both which have been important steps towards a more cost-effective solution.     

Confirmatory analysis of steroids in muscle using liquid chromatography-tandem mass spectrometry

A method is described for screening and confirmation of synthetic and endogenous steroids in muscle tissue. The method is sensitive, selective, and rapid and the consumption of organic solvents is low, compared to previously published methods. The procedure involves hydrolysis, defattening with heptane and final clean up with SPE using C(18) cartridge. After filtration, the analytes are analysed by LC/MS/MS and quantification is performed using deuterated internal standards. Decision limits (CCα) varied from 0.02 to 0.33 μg kg(-1) and the detection capabilities (CCβ) were <0.50 μg kg(-1). The mean within-laboratory reproducibility ranged 5-22% (%RSD(IR)). Endogenous steroids (e.g. testosterone, epitestosterone and androstenedione) have been included in the method, to provide an insight into their levels, as the presence of these steroids was detected several times during analysis of imported meat.