Improving the conductance of carbon nanotube networks through resonant momentum exchange

We present a mechanism to improve the conductivity of carbon nanotube (CNT) networks by improving the conductance between CNTs of different chirality. We argue generally that a weak perturbation can greatly improve the inter-tube conductance by allowing momentum-conserving tunnelling. The mechanism is verified with a tight-binding model, allowing an investigation of its impact for a network containing a range of chiralities. We discuss practical implementations, and conclude that it may be effected by weak physical interactions, and therefore does not require chemical bonding to the CNTs.Comment: 6 pages, 4 figure

Retire Later or Work Harder?

We compare two policies of increasing British state pension provision: (a) increase the pensionable age of men and women, (b) maintain the existing retirement age but require older workers to work longer per-period hours. There are reasons for policy makers to give serious consideration to the under-researched alternative (b). First, from wage - hours contract theory we know that there are potential gains to both workers and firms of allowing hours to rise in work experience. Second, there is strong evidence that job satisfaction rises in age. Third, there has in any case been a significant overall increase in the hours supplied by older workers in the last two decades. We review the relevant theory, model the trade-off between later retirement versus increased work intensity, produce relevant background facts, and provide estimates of the policy trade-offs.older workers, statutory retirement age, hours of work

On properties of the n-dimensional norm residue symbol in higher local class field theory

AbstractLet k be a finite extension of Qp which contains the roots of unity μ. Here ¦μ¦ = q = pu, p ≠ 2. We consider an n-dimensional local field given explicitly as a power series in n − 1 variables by Xn = k t1… tn−1. The norm residue symbol has been generalized by Vostokov for mixed characteristic local fields X = t1 tn−1 of dimension n. It is a non-degenerate pairing given by Kn(X)(Kn(X))q × X∗(X∗)q → μ where Kn(X) is the nth Milnor K-group of X = Xn and X∗ is the multiplicative group of X. It is shown here that the Vostokov pairing on the n-dimensional local field Xn = k t1 tn−1 commutes with the Vostokov pairing on the n − 1 dimensional local field Xn − 1 = k t1 tn − 2. We achieve this by constructing a map M which projects the roots of unity from the pairing on X = Xn onto the roots of unity from the pairing on Xn − 1

Negativity and contextuality are equivalent notions of nonclassicality

Two notions of nonclassicality that have been investigated intensively are: (i) negativity, that is, the need to posit negative values when representing quantum states by quasiprobability distributions such as the Wigner representation, and (ii) contextuality, that is, the impossibility of a noncontextual hidden variable model of quantum theory (also known as the Bell-Kochen-Specker theorem). Although both of these notions were meant to characterize the conditions under which a classical explanation cannot be provided, we demonstrate that they prove inadequate to the task and we argue for a particular way of generalizing and revising them. With the refined version of each in hand, it becomes apparent that they are in fact one and the same. We also demonstrate the impossibility of noncontextuality or nonnegativity in quantum theory with a novel proof that is symmetric in its treatment of measurements and preparations.Comment: 5 pages, published version (modulo some supplementary material

Retire Later or Work Harder?

We compare two policies of increasing British state pension provision: (a) increase the pensionable age of men and women, (b) maintain the existing retirement age but require older workers to work longer per-period hours. There are reasons for policy makers to give serious consideration to the under-researched alternative (b). First, from wage - hours contract theory we know that there are potential gains to both workers and firms of allowing hours to rise in work experience. Second, there is strong evidence that job satisfaction rises in age. Third, there has in any case been a significant overall increase in the hours supplied by older workers in the last two decades. We review the relevant theory, model the trade-off between later retirement versus increased work intensity, produce relevant background facts, and provide estimates of the policy trade-offs

Silicon Nanocrystal Field-Effect Light-Emitting Devices

We describe the operation of a light-emitting device in which silicon nanocrystals are electrically pumped via the field-effect electroluminescence (EL) mechanism. In contrast to the simultaneous bipolar carrier injection used in conventional p-n junction light-emitting diodes, this device employs sequential unipolar programming of both electrons and holes across a tunneling barrier from the same semiconductor channel. Light emission is strongly correlated with the injection of second carriers into nanocrystals that have been previously programmed with charges of the opposite sign. The properties of this device are well described by the model of a charge injection through Coulomb field modified tunneling processes. We additionally consider limiting performance bounds for potential future devices fabricated from nanocrystals with different radiative emission rates

Imaging with a small number of photons

Low-light-level imaging techniques have application in many diverse fields, ranging from biological sciences to security. We demonstrate a single-photon imaging system based on a time-gated inten- sified CCD (ICCD) camera in which the image of an object can be inferred from very few detected photons. We show that a ghost-imaging configuration, where the image is obtained from photons that have never interacted with the object, is a useful approach for obtaining images with high signal-to-noise ratios. The use of heralded single-photons ensures that the background counts can be virtually eliminated from the recorded images. By applying techniques of compressed sensing and associated image reconstruction, we obtain high-quality images of the object from raw data comprised of fewer than one detected photon per image pixel.Comment: 9 pages, 4 figure

Translocation of reindeer from South Georgia to the Falkland Islands

This report describes the first translocation of reindeer Rangifer tarandus from South Georgia to the Falkland Islands, in the South Atlantic Ocean. Reindeer were introduced from Norway to the subantarctic island of South Georgia on three occasions in the early 1900s by Norwegian whalers, and today they exist as two discrete herds, numbering approximately 2600 individuals in total. Because of concerns over the impact on native vegetation, the long-term eradication of reindeer from South Georgia has recently been proposed. A translocation of reindeer to the Falkland Islands was undertaken in 2001 by the Falkland Island Government with two objectives: (1) to preserve the genetic resources of at least one of the South Georgia herds; and (2) to facilitate the diversification of the agricultural sector of the Falkland Islands by establishing a commercial reindeer herd. Techniques developed and used in North America for the successful relocation of large numbers of calves were adopted for the translocation. A total of 59 calves (26 females and 33 males) were successfully translocated from South Georgia to the Falklands Islands in 2001, and subsequently produced their first offspring in 2003. Good husbandry practices and an understanding of biology and behaviour are essential for the successful translocation of reindeer.Flytting av rein fra Sør-Georgia til FalklandsøyeneAbstract in Norwegian / Sammendrag: Artikkelen beskriver den første overføring av rein Rangifer tarandus fra Sør-Georgia til Falklandsøyene i søratlanteren. Tamrein fra Norge ble flyttet til den subarktiske øya Sør-Georgia ved tre anledninger i perioden 1911 til 1925 i forbindelse med den norske hvalfangsten der. I dag består bestanden av rundt regnet 2600 dyr fordelt på to geografisk atskilte flokker. Av hensyn til den naturlige vegetasjonen på øya er det forslag om å på sikt utrydde reinbestanden på øya. Regjeringen på Falklandsøyene foretok en første overføring av rein fra Sør-Georgia i 2001 ut fra en målsetting om å 1) bevare genetiske ressurser fra minst en av de to reinflokkene, og 2) øke mulighetene innenfor landbrukssektoren på Falklandsøyene ved å etablere en kommersiell reinflokk der. Overføringen ble utført med metoder som hadde vist seg formålstjenlige ved flytting og nylokalisering av kalver i Nord-Amerika. Totalt ble 59 kalver overført i 2001 derav 26 hunndyr. De overførte reinene produserte kalver i 2003. God driftspraksis og biologisk og atferdsmessig forståelse var viktig for en vellykket overføring

Harvest-based Monitoring in the Inuvialuit Settlement Region: Steps for Success

We define harvest-based monitoring as the long-term collection of data or samples from a subsistence harvest in order to reveal, document, and track changes in biophysical resources. Our objective is to describe five practical steps that have guided us over the past two decades during delivery of harvest-based monitoring studies in the Inuvialuit Settlement Region (ISR). Studies have usually been designed to detect (but not necessarily explain) change, to involve local harvesters, and to incorporate indigenous and science-based knowledge. The five steps are to (1) formulate a scientific research or long-term monitoring question that can reasonably be answered by analyzing data from harvests or harvested specimens, (2) design the program according to scientific and indigenous protocols, (3) determine respective partner roles for delivery of the field program, (4) conduct the field work, and (5) analyze data and communicate results. At all steps, it is important to ensure that science and indigenous knowledge partners respect and trust each other’s skills, knowledge, and abilities; that regular communication is fostered; and that provisions are in place to monitor progress. The credible blending of indigenous and scientific views and skills improves the likelihood of ultimately understanding the resource, its habitats, and its inherent ecological relationships.Key words: harvest-based monitoring, Inuvialuit Settlement Region, collaborative research, participatory researchNous définissons la surveillance des captures comme la collecte à long terme de données ou d’échantillons provenant des captures ou récoltes de subsistance et ce, dans le but de révéler, de documenter et de suivre les changements caractérisant les ressources biophysiques. Notre objectif consiste à décrire cinq étapes pratiques qui nous ont servi de guides ces deux dernières décennies dans le cadre d’études de surveillance des captures dans la région désignée des Inuvialuit (RDI). Habituellement, les études sont conçues pour détecter (et non pas nécessairement pour expliquer) le changement, pour faire appel aux personnes faisant les captures dans la région et pour favoriser l’intégration des connaissances indigènes et scienti­fiques. Ces cinq étapes sont les suivantes : 1) formuler une question de recherche scientifique ou de surveillance à long terme à laquelle on peut raisonnablement répondre au moyen de l’analyse des données de captures ou des échantillons capturés; 2) concevoir un programme qui respecte les protocoles scientifiques et indigènes; 3) déterminer le rôle des partenaires respectifs en ce qui a trait à l’exécution du programme sur le terrain; 4) réaliser le travail sur le terrain; et 5) analyser les données puis communiquer les résultats. À toutes ces étapes, il est important de faire en sorte que les partenaires en matière de connaissances scientifiques et de connaissances indigènes respectent les compétences, les connaissances et les aptitudes de chacun, et se fassent confiance; que les partenaires communiquent régulièrement; et que des dispositions soient en place pour suivre les progrès. Le mélange crédible de points de vue et de compétences indigènes et scientifiques améliore la probabilité que l’on finisse par comprendre la ressource, ses habitats et ses relations écologiques inhérentes. Mots clés : surveillance des captures, région désignée des Inuvialuit, recherche collaborative, recherche participativ

The 67 Hz Feature in the Black Hole Candidate GRS 1915+105 as a Possible ``Diskoseismic'' Mode

The Rossi X-ray Timing Explorer (RXTE) has made feasible for the first time the search for high-frequency (~ 100 Hz) periodic features in black hole candidate (BHC) systems. Such a feature, with a 67 Hz frequency, recently has been discovered in the BHC GRS 1915+105 (Morgan, Remillard, & Greiner). This feature is weak (rms variability ~0.3%-1.6%), stable in frequency (to within ~2 Hz) despite appreciable luminosity fluctuations, and narrow (quality factor Q ~ 20). Several of these properties are what one expects for a ``diskoseismic'' g-mode in an accretion disk about a 10.6 M_sun (nonrotating) - 36.3 M_sun (maximally rotating) black hole (if we are observing the fundamental mode frequency). We explore this possibility by considering the expected luminosity modulation, as well as possible excitation and growth mechanisms---including turbulent excitation, damping, and ``negative'' radiation damping. We conclude that a diskoseismic interpretation of the observations is viable.Comment: 4 Pages, Latex (emulateapj.sty included), to Appear in ApJ Letters, Vol. 477, Final Version with Updated Reference