Excitation, dynamics and dephasing in quantum dots

This paper concerns the femtosecond dynamical relaxation of excited states in quantum dots or clusters. The clusters are typically polar, consisting of 150-200 atoms, and are of interest for potential photonic devices. Our work identifies certain novel effects, 'dynamic dilation' and 'ringing', associated with excited states of non-metallic dots of this size. Dynamic dilation occurs for dots at constant pressure, rather than constant volume. Dilation induces a modest but significant energy shift on a picosecond timescale, slower than the characteristic vibrational period of the configuration coordinate. The magnitude of the shift is clearly size dependent, tending to zero in the limit of a bulk system. This shift can be equivalent to dephasing, and may explain one component of dephasing already experimentally observed. Such dephasing may also affect the usefulness of dots in ultrafast optical switching. The second novel effect associated with the clusters is the relatively long-lived vibrational excitation of the dot leading to 'ringing'. This is strongly sensitive to the acoustic mismatch with the environment. Neither 'dynamic dilation' nor 'ringing' are especially sensitive to the composition of the dots, or to whether the excited states correspond closely to bulk excitons or to defect states, and hence need to be taken into account in the excitation of quantum dots

On the Solutions of Generalized Bogomolny Equations

Generalized Bogomolny equations are encountered in the localization of the topological N=4 SYM theory. The boundary conditions for 't Hooft and surface operators are formulated by giving a model solution with some special singularity. In this note we consider the generalized Bogomolny equations on a half space and construct model solutions for the boundary 't Hooft and surface operators. It is shown that for the 't Hooft operator the equations reduce to the open Toda chain for arbitrary simple gauge group. For the surface operators the solutions of interest are rational solutions of a periodic non-abelian Toda system.Comment: 16 pages, no figure

High-status lobbyists are most likely to overrate their success

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record Overconfidence helps individuals reach higher status within social groups by making them seem more competent regardless of objective ability, so this bias may be especially prevalent among status-oriented members of elite communities. Based on this premise, we explore whether lobbyists in the USA misperceive their success. Using models that (1) control for legislative outcome when predicting self-assessed policy success and (2) compare self-assessed policy success on specific proposals against the average success reported by all lobbyists working on the same side of an issue, we identify systematic tendencies to overrate achievements. Lobbyists with higher incomes, who reside in Washington, DC, USA, have congressional experience and who engage in a broader range of activities are more likely to overrate their success. Public interest group lobbyists tend to underestimate success. We conclude that political elites are subject to the same biases as others when evaluating their performance, and these biases may be largely status-driven.European Research Counci

Fast Scalable Construction of (Minimal Perfect Hash) Functions

Recent advances in random linear systems on finite fields have paved the way for the construction of constant-time data structures representing static functions and minimal perfect hash functions using less space with respect to existing techniques. The main obstruction for any practical application of these results is the cubic-time Gaussian elimination required to solve these linear systems: despite they can be made very small, the computation is still too slow to be feasible. In this paper we describe in detail a number of heuristics and programming techniques to speed up the resolution of these systems by several orders of magnitude, making the overall construction competitive with the standard and widely used MWHC technique, which is based on hypergraph peeling. In particular, we introduce broadword programming techniques for fast equation manipulation and a lazy Gaussian elimination algorithm. We also describe a number of technical improvements to the data structure which further reduce space usage and improve lookup speed. Our implementation of these techniques yields a minimal perfect hash function data structure occupying 2.24 bits per element, compared to 2.68 for MWHC-based ones, and a static function data structure which reduces the multiplicative overhead from 1.23 to 1.03

The use of β-cell transcription factors in engineering artificial β cells from non-pancreatic tissue

Type 1 diabetes results from the autoimmune destruction of the insulin-producing pancreatic beta (β) cells. Patients with type 1 diabetes control their blood glucose levels using several daily injections of exogenous insulin; however, this does not eliminate the long-term complications of hyperglycaemia. Currently, the only clinically viable treatments for type 1 diabetes are whole pancreas and islet transplantation. As a result, there is an urgent need to develop alternative therapies. Recently, cell and gene therapy have shown promise as a potential cure for type 1 diabetes through the genetic engineering of 'artificial' β cells to regulate blood glucose levels without adverse side effects and the need for immunosuppression. This review compares putative target cells and the use of pancreatic transcription factors for gene modification, with the ultimate goal of engineering a glucose-responsive 'artificial' β cell that mimics the function of pancreatic β cells, while avoiding autoimmune destruction

Forms of iron in soils on basement complex rocks of Kaduna state in northern guinea Savanna of Nigeria

The forms of iron extracted by different methods were studied in soils developed on four basement complex rocks within Northern Guinea Savanna of Nigeria namely: migmatite gneisses, older granite, quartzites and mica schists. The study shows that forms of iron generally decreased in the order of total elemental iron (FeT) determined by XRF > double acid extractable total iron (Fea) > dithionite extractable iron oxide (Fed) > oxalate extractable iron oxide (Fex) > pyrophosphate extractable iron oxide (Fep) > 0.1M HCl extractable micronutrient available iron (Feh). Variation in content of total irons (FeT and Fea) were not significant in the soils, but content of Feh, Fed, Fex and Fex/d significantly varied in the soils on the various parent materials. Therefore processes and extent of pedogenesis were considered to influence the variations resulting in recrystallization and increase in content of Feh and Fed in these soils. The significant correlation between various forms of Fe (Fea, Fed, and Fex) with active iron ratio further affirmed that as soils on basement complexes increase in their pedogenetic age, Fe content generally increases irrespective of total forms of iron. The strong correlation between FeT, Fea and Fed indicate that these forms of iron were extracted from similar sources.Keywords: Iron, basement complex rock, pedogenesis, Northern Guinea Savanna, Nigeria

Pioneers in CNS inhibition: 2. Charles Sherrington and John Eccles on inhibition in spinal and supraspinal structures

This article reviews the contributions of the English neurophysiologist, Charles Scott Sherrington [1857–1952], and his Australian PhD trainee and collaborator, John Carew Eccles [1903–1997], to the concept of central inhibition in the spinal cord and brain. Both were awarded Nobel Prizes; Sherrington in 1932 for “discoveries regarding the function of neurons,” and Eccles in 1963 for “discoveries concerning the ionic mechanisms involved in excitation and inhibition in central portions of the nerve cell membrane.” Both spoke about central inhibition at their Nobel Prize Award Ceremonies. The subsequent publications of their talks were entitled “Inhibition as a coordinative factor” and “The ionic mechanism of postsynaptic inhibition”, respectively. Sherrington's work on central inhibition spanned 41 years (1893–1934), and for Eccles 49 years (1928–1977). Sherrington first studied central inhibition by observing hind limb muscle responses to electrical (peripheral nerve) and mechanical (muscle) stimulation. He used muscle length and force measurements until the early 1900s and electromyography in the late 1920s. Eccles used these techniques while working with Sherrington, but later employed extracellular microelectrode recording in the spinal cord followed in 1951 by intracellular recording from spinal motoneurons. This considerably advanced our understanding of central inhibition. Sherrington's health was poor during his retirement years but he nonetheless made a small number of largely humanities contributions up to 1951, one year before his death at the age of 94. In contrast, Eccles retained his health and vigor until 3 years before his death and published prolifically on many subjects during his 22 years of official retirement. His last neuroscience article appeared in 1994 when he was 91. Despite poor health he continued thinking about his life-long interest, the mind-brain problem, and was attempting to complete his autobiography in the last years of his life

Weed management in banana production: The use of Nelsonia canescens (Lam.) Spreng as a nonleguminous cover crop

During a survey of weeds in the Tiko banana plantations, the plant Nelsonia canescens (Lam.) Spreng was found to have invaded large areas of the plantation with no visible adverse effects on the banana crop. The effects of this Acanthaceae on banana yield parameters, snails’ population and weed species diversity and abundance were evaluated, with the intension of recommending the plant as a cover crop in weed management in banana plantations. Of the 73 weed species identified in Tiko banana plantation, only nine were found growing in association with N. canescens. These weed species also showed reduced abundance and vigour. The reduction in abundance ranged from 60 to 100%. The reduction in abundance was more pronounced during the dry season when cover crop growth was dense, than in the rainy season when there was reduced growth. The pseudo - stem circumference, bunch weight and hand class were significantly higher (p > /0.05) for plants grown with cover crop than for those grown without. The number of snails on and around the pseudo - stem was also significantly reduced in banana grown with N. canescens cover crop than in plants grown without. N. canescens has an added advantage in that it is prostrate and does not climb on the banana pseudo - stem. This may be a good alternative weed management tool in banana production. The techniques of mass production need to be developed

Biological activities (anti-inflammatory and anti-oxidant) of fractions and methanolic extract of Philonotis hastate (Duby Wijk & MargaDant).

Background: Bryophytes like other lower plants (non-vascular plants) are not traditionally employed for therapeutic purposes. Hence this study evaluated the in vitro anti-oxidant potentials and anti-inflammatory activities of the fractions and methanolic extract of Moss (Philonotis hastata, Duby) with a view to studying its biological activities.Methods: Plant materials were collected, identified, dried, pulverized and extracted with 70% (v/v) methanol to afford methanolic extract (ME). The ME was fractionated using solvent of increasing polarity and followed by phytochemical screening of the extract and fractions. The anti-oxidant potentials (total phenolics and flavonoids), anti-oxidant activities (DPPH-radical scavenging, reductive power, hydroxyl radical scavenging and ABTS+ radical scavenging) and anti-inflammatory activity (red blood stabilizing) of the extract and fractions were investigated.Results: Phytochemicals detected included alkaloids, steroids and cardiac glycosides. The fractions and methanolic extract exhibited moderate antioxidant potentials with various models. The flavonoid contents of the methanol extract and fractions ranged between 1.70 ± 0.05 and 129.70 ± 1.00 mg/g extract RE (Rutin Equivalent) and total phenol content ranged between 1.84 ± 0.62 and 136.25 ± 0.18 mg/g extract TAE (Tannic Acid Equivalent). The reductive power activity ranged between 5.71 ± 0.02 and 40.40 ± 0.30 mg/g Vitamin C equivalent, the hydroxyl radical scavenging (15.54 ± 0.02 to 30.07± 0.29 %), and the ABTS+- radical scavenging activity (11.59 ± 2.85 to 40.50 ± 1.35%). The membrane stabilizing potentials of the fractions and extract (methanol) ranged between 19.19 ± 2.66% and 78.26 ± 2.60%. The activities were comparable to standard antiinflammatory drugs and chemicals.Conclusion: It could be concluded that the fractions and methanol extract of P. hastata exhibit moderate, potent and appreciable anti-oxidant and anti-inflammatory activities with aqueous and ethyl acetate fractions elicited highest activities. As such, bryophytes possess therapeutic potentials and could be employed in the treatment and management of anti-oxidant and anti-inflammatory disorders.Key words: Philonotis hastata, bryophytes, membrane - stabilizing, flavonoids, anti-oxidant, anti-inflammatory