Probing millisecond pulsar emission geometry using light curves from the Fermi Large Area Telescope

An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from 3D emission modeling, including the Special Relativistic effects of aberration and time-of-flight delays and also rotational sweepback of B-field lines, in the geometric context of polar cap (PC), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly-rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by TPC and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production -- even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We also find exclusive differentiation of the current gamma-ray MSP population into two MSP sub-classes: light curve shapes and lags across wavebands impose either pair-starved PC (PSPC) or TPC / OG-type geometries. In the first case, the radio pulse has a small lag with respect to the single gamma-ray pulse, while the (first) gamma-ray peak usually trails the radio by a large phase offset in the latter case. Finally, we find that the flux correction factor as a function of magnetic inclination and observer angles is typically of order unity for all models. Our calculation of light curves and flux correction factor for the case of MSPs is therefore complementary to the "ATLAS paper" of Watters et al. for younger pulsars.Comment: 51 pages, 23 figures, 3 tables; low-resolution figures; accepted for publication by Ap

Kierkegaard se, drei grossen ideen” en die ini- siasie van henry van eeden (sewe dae b y die silbersteins)

Die doel van Henry se verblyf by die Silbersteins word vroeg in Sewe dae verwoord as Jock tydens die eerste aandbyeenkoms sê dat Henry „van sekere gevestigde idees” (p. 16) ontslae moet raak. Ook mrs. Silberstein beskou dit as noodsaaklik dat sy on­ skuld vemietig moet word (p. 22). Op die oggendwandeling van die tweede dag herhaal Jock sy stelling van die vorige aand en voeg daaraan toe dat daar baie dinge is wat Henry ,,sal moet leer en verleer” (p. 28). Vir die modeme mens, wat „van die vrug van kennis geëet” het, is daar „geen illussies meer nie” (p. 32)

COMMUNITY STRATEGIES IN THE AZTEC IMPERIAL FRONTIER: PERSPECTIVES FROM TOTOGAL, VERACRUZ, MEXICO

Using archaeological and ethnohistorical data, this dissertation examines the character of the relationship between the Late Postclassic (ca. AD 1250-1520) frontier center of Totogal, located in the western Tuxtla Mountains (Toztlan) of southern Veracruz, Mexico, and the expanding Aztec Empire. Traditional models of imperialism examine frontiers from a core perspective that limits the autonomy and agency of groups in the path of expansion. Recent ethnographic, ethnohistoric, and archaeological studies of other boundaries, however, suggest that considerable room for negotiation exists within the space of interactions, whether asymmetrical amounts of power characterize the home bases of those groups. I argue that elites at Totogal, using imperial symbols and markers of their own high status, sponsored feasts and rituals for the non-elite public, during which they brokered the potentially conflicting interests of the Aztecs and the tribute paying population of the Tuxtlas. The invitation of the public to feasts and rituals that combined imperial and local elite symbols (and possibly green obsidian), naturalized the relationship between local elites and imperial representatives with non-elite occupants of Totogal and nearby settlements by establishing a reciprocal system of gifting whereby food and drink, served in the context of elaborate religious and commensal rituals, provided a benefit to the Tuxteco public which, along with other exotic highland goods, was viewed as an acceptable exchange for the local tribute items that the empire desired. This study is an important application of current anthropological perspectives on boundaries, borders, and frontiers to the Aztec Empire. It is also a critical examination of the types of strategies individuals and groups living in boundary regions can enact in situations of contact and change. While studies of modern groups in boundary regions have addressed identity construction and manipulation, and other dynamic social, political, and cultural processes that take place, they do not typically or systematically examine how the negotiations that are enacted in boundary zones are materialized—how changing identities are represented symbolically through the use of particular products or consumption patterns. It is in this area that archaeological perspectives on boundary zone interactions can make important contributions to the modern world

Hardy's Inequality for the fractional powers of Grushin operator

We prove Hardy's inequality for the fractional powers of the generalized sublaplacian and the fractional powers of the Grushin operator. We also find an integral representation and a ground state representation for the fractional powers of generalized sublaplacian

Bacterial contamination of re-usable laryngoscope blades during the course of daily anaesthetic practice

Background and objectives. Hospital-acquired infections (HAIs) are largely preventable through risk analysis and modification of practice.Anaesthetic practice plays a limited role in the prevention of HAIs, although laryngoscope use and decontamination is an area of concern.We aimed to assess the level of microbial contamination of re-usable laryngoscope blades at a public hospital in South Africa.Setting. The theatre complex of a secondary-level public hospital in Johannesburg.Methods. Blades from two different theatres were sampled twice daily, using a standardised technique, over a 2-week period. Samples werequantitatively assessed for microbial contamination, and stratified by area on blade, theatre and time using Fisher’s exact test.Results. A contamination rate of 57.3% (63/110) was found, with high-level contamination accounting for 22.2% of these. Commoncommensals were the most frequently isolated micro-organisms (79.1%), but important hospital pathogens such as Enterobacter species and Acinetobacter baumannii were isolated from blades with high-level contamination. No significant difference in the level of microbial contamination by area on blade, theatre or time was found (p<0.05).Conclusions. A combination of sub-optimal decontamination and improper handling of laryngoscopes after decontamination results in significant microbial contamination of re-usable laryngoscope blades. There is an urgent need to review protocols and policies surrounding the use of these blades