5,033 research outputs found
Electronic properties of linear carbon chains: resolving the controversy
Literature values for the energy gap of long one-dimensional carbon chains
vary from as little as 0.2 eV to more than 4 eV. To resolve this discrepancy,
we use the GW many-body approach to calculate the band gap of an infinite
carbon chain. We also compute the energy dependence of the attenuation
coefficient governing the decay with chain length of the electrical
conductance of long chains and compare this with recent experimental
measurements of the single-molecule conductance of end-capped carbon chains.
For long chains, we find eV and an upper bound for of
\AA.Comment: Accepted for publication in Journal of Chemical Physic
Profiling I/O interrupts in modern architectures
Journal ArticleAs applications grow increasingly communication-oriented, interrupt performance quickly becomes a crucial component of high performance I/O system design. At the same time, accurately measuring interrupt handler performance is difficult with the traditional simulation, instrumentation, or statistical sampling approaches. One o f the most important components o f interrupt performance is cache behavior. This paper presents a portable method for measuring the cache effects o f I/O interrupt handling using native hardware performance counters. To provide a portability stress test, the method is demonstrated on two commercial platforms with different architectures, the SGI Origin 200 and the Sun LJltra-1. This case study uses the methodology to measure the overhead of the two most common forms o f interrupt traffic: disk and network interrupts. The study demonstrates that the method works well and is reasonably robust. In addition, the results show that disk interrupts behave similar on both platforms, while differences in OS organization cause network interrupts to behave very differently. Furthermore, network interrupts exhibit significantly larger cache footprints.
TESTING FOR NONCOMPETITIVE BEHAVIOR IN THE U.S. FOOD INDUSTRY
Market structure is tested in 47 subsectors of the US food industry between 1958-1994. All industries exert market power in at least some of the sample years. Deadweight loss estimates resulting from noncompetitive behavior ranging from over 1 million in the malt industry.Agribusiness, Marketing,
Capturing the industrial requirements of set-based design for CONGA framework
The Configuration Optimisation of Next-Generation Aircraft (CONGA) is a proposed framework in a response industrial need to enhance the aerospace capability in the UK. In order to successfully address this challenge, a need to develop a true multi-disciplinary Set-Based Design (SBD) capability that could deploy new technologies on novel configurations more quickly and with greater confidence was identified. This paper presents the first step towards the development of the SBD capabilities which is to elicit the industrial requirement of the SBD process for the key aerospace industrial partners involved in this CONGA approach
A Rentier State under Blockade: Qatarâs Water-Energy-Food Predicament from Energy Abundance and Food Insecurity to a Silent Water Crisis
This article investigates Qatarâs sustainability crisis of the high levels of water, electricity and food use. The high levels of consumption have been enabled by Qatarâs significant hydrocarbons wealth, a generous rentier stateâs redistributive water governance, and structural dependence on imported food and food production subsidies. The water crisis is silent because it does not generate supply disruptions nor any public discontentment. The geopolitical blockade Qatar is experiencing sparked discussions in policy circles on the best ways to ensure food security, but has only exacerbated its water insecurity. The blockade makes more urgent than ever the necessity to maximize and increase synergies among different sectors
Capturing the Industrial Requirements of Set-Based Design for the CONGA Framework
The Configuration Optimisation of Next-Generation Aircraft (CONGA) is a proposed framework in a response to industrial need to enhance the aerospace capability in the UK. In order to successfully address this challenge, a need to develop a true multi-disciplinary Set-Based Design (SBD) capability that could deploy new technologies on novel configurations more quickly and with greater confidence was identified. This paper presents the first step towards the development of the SBD capabilities which is to elicit the industrial requirement of the SBD process for the key aerospace industrial partners involved in this CONGA approach
A new approach to materials discovery for electronic and thermoelectric properties of single-molecule junctions
We have investigated a large set of symmetric and asymmetric molecules to demonstrate a general rule for molecular-scale quantum transport, which provides a new route to materials design and discovery. The rule states âthe conductance GXBY of an asymmetric molecule is the geometric mean of the conductance of the two symmetric molecules derived from it and the thermopower SXBY of the asymmetric molecule is the algebraic mean of their thermopowersâ. The studied molecules have a structure X-B-Y, where B is the backbone of the molecule, while X and Y are anchor groups, which bind the molecule to metallic electrodes. When applied to experimentally-measured histograms of conductance and thermopower, the rules apply to the statistically-most-probable values. We investigated molecules with anchors chosen from the following family: cyano, pyridl, dihydrobenzothiol, amine and thiol. For the backbones B, we tested fourteen different structures. We found that the formulae (GXBY)2 = GXBX*GYBY and SXBY=(SXBX+SYBY)/2 were satisfied in the large majority of the cases, provided the Fermi energy is located within the HOMO-LUMO gap of the molecules. The circuit rules imply that if measurements are performed on molecules with nA different anchors and nB different backbones, then properties of nA(nA+1)nB/2 molecules can be predicted. So for example, in the case of 20 backbones and 10 anchors, 30 measurements (or reliable calculations) can provide a near quantitative estimate for 1070 measurements of other molecules, no extra cost
Oral cancer stem cells drive tumourigenesis through activation of stromal fibroblasts
Background
Cancer stem cells are responsible for tumour progression and chemoresistance. Fibroblasts surrounding a tumour also promote progression and fibroblast âactivationâ is an independent prognostic marker in oral cancer. Cancer stem cells may therefore promote tumourigenesis through communication with stromal fibroblasts.
Methods
Cancer stem cells were isolated from oral cancer cell lines by adherence to fibronectin or cisplatin resistance. Fibroblasts were exposed to conditioned medium from these cells, and the activation markers, alpha smooth muscle actin and interleukinâ6, were assessed using qPCR and immunofluorescence. Stem cell markers and smooth muscle actin were examined in oral cancer tissue using immunohistochemistry.
Results
Adherent and chemoresistant cells expressed increased levels of stem cell markers CD24, CD44 and CD29 compared with unsorted cells. Adherent cells exhibited lower growth rate, higher colony forming efficiency and increased cisplatin resistance than unsorted cells. Smooth muscle actin and Interleukinâ6 expression were increased in fibroblasts exposed to conditioned medium. In oral cancer tissue, there was a positive correlation between expression of ÎąSMA and stem cell markers.
Conclusions
Adherence to fibronectin and chemoresistance isolates stemâlike cells that can activate fibroblasts, which together with a correlation between markers of both in vivo, provides a mechanism by which such cells drive tumourigenesis
Exploiting the Extended {\pi}-System of Perylene Bisimide for Label-free Single-Molecule Sensing
We demonstrate the potential of perylene bisimide (PBI) for label-free
sensing of organic molecules by investigating the change in electronic
properties of five symmetric and asymmetric PBI derivatives, which share a
common backbone, but are functionalised with various bay-area substituents.
Density functional theory was combined with a Greens function scattering
approach to compute the electrical conductance of each molecule attached to two
gold electrodes by pyridyl anchor groups. We studied the change in their
conductance in response to the binding of three analytes, namely TNT, BEDT-TTF
and TCNE, and found that the five different responses provided a unique
fingerprint for the discriminating sensing of each analyte. This ability to
sense and discriminate was a direct consequence of the extended {\pi} system of
the PBI backbone, which strongly binds the analytes, combined with the
different charge distribution of the five PBI derivatives, which leads to a
unique electrical response to analyte binding.Comment: J. Mater. Chem. C, 201
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