12,815 research outputs found
The impact of the warm outflow in the young (GPS) radio source & ULIRG PKS 1345+12 (4C 12.50)
(Abridged) We present new deep VLT/FORS optical spectra with intermediate
resolution and large wavelength coverage of the GPS radio source and ULIRG
PKS1345+12 (4C12.50; z=0.122), taken with the aim of investigating the impact
of the nuclear activity on the circumnuclear ISM. PKS1345+12 is a powerful
quasar and is also the best studied case of an emission line outflow in a
ULIRG. Using the density sensitive transauroral emission lines [S II]4068,4076
and [O II]7318,7319,7330,7331, we pilot a new technique to accurately model the
electron density for cases in which it is not possible to use the traditional
diagnostic [S II]6716/6731, namely sources with highly broadened complex
emission line profiles and/or high (Ne > 10^4 cm^-3) electron densities. We
measure electron densities of Ne=2.94x10^3 cm^-3, Ne=1.47x10^4 cm^-3 and
Ne=3.16x10^5 cm^-3 for the regions emitting the narrow, broad and very broad
components respectively. We calculate a total mass outflow rate of 8 M_sun
yr^-1. We estimate the total mass in the warm gas outflow is 8x10^5 M_sun. The
total kinetic power in the warm outflow is 3.4x10^42 erg s^-1. We find that
only a small fraction (0.13% of Lbol) of the available accretion power is
driving the warm outflow, significantly less than currently required by the
majority of quasar feedback models (~5-10\% of Lbol), but similar to recent
findings by Hopkins et al. (2010) for a two-stage feedback model. The models
also predict that AGN outflows will eventually remove the gas from the bulge of
the host galaxy. The visible warm outflow in PKS1345+12 is not currently
capable of doing so. However, it is entirely possible that much of the outflow
is either obscured by a dense and dusty natal cocoon and/or in cooler or hotter
phases of the ISM. This result is important not just for studies of young
(GPS/CSS) radio sources, but for AGN in general.Comment: Accepted for publication in MNRAS. 11 pages, 4 figure
Gas outflows in radio galaxies
We present a summary of our recent results on gas outflows in radio galaxies.
Fast outflows (up to 2000 km/s) have been detected both in ionized and neutral
gas. The latter is particularly surprising as it shows that, despite the
extremely energetic phenomena occurring near an AGN, some of the outflowing gas
remains, or becomes again, neutral. These results are giving new and important
insights on the physical conditions of the gaseous medium around an AGN.Comment: To appear in the proceedings of the IAU Symposium #217, Recycling
Intergalactic and Interstellar Matter, eds. P.-A. Duc, J. Braine, and E.
Brinks, 6 pages. The full paper with high resolution images can be downloaded
from http://www.astron.nl/~morganti/Papers/outflows.ps.g
Transparent yttrium hydride thin films prepared by reactive sputtering
Metal hydrides have earlier been suggested for utilization in solar cells.
With this as a motivation we have prepared thin films of yttrium hydride by
reactive magnetron sputter deposition. The resulting films are metallic for low
partial pressure of hydrogen during the deposition, and black or
yellow-transparent for higher partial pressure of hydrogen. Both metallic and
semiconducting transparent YHx films have been prepared directly in-situ
without the need of capping layers and post-deposition hydrogenation. Optically
the films are similar to what is found for YHx films prepared by other
techniques, but the crystal structure of the transparent films differ from the
well-known YH3 phase, as they have an fcc lattice instead of hcp
Managing Queuing Problems Through Online Booking System
Queuing is one of the important issues to the service industry due to its impact towards the operations capabilities and customer satisfaction of the organization. The determination of how long a customer should wait for a product or service has long been a major concern for service management specialists who bear the trade-off between minimizing operation costs incurred in optimizing the configuration of a queue system, as well as, minimizing the cost of queuing of the customers. As the current economies progressively changing into a service dominated one, it is essential to thoroughly understand the know-how to effectively deal with queuing lines to improve customer satisfaction of service. Fast food restaurants are popular among price-sensitive youths and working adults who value the conducive environment and convenient services. McDonald’s chains of restaurants promote their sales by offering package meals which are perceived to be inexpensive. These promotional meals attract good response, resulting in occasional long queues and inconvenient queuing times. However, customers are willing to queue and pay to get food. Restaurants should avoid losing their customers due to a long wait on the line. It is because people today demand not only for quality food but also for speed. Fast food restaurant players explore on the approaches to optimize the efficiency of restaurant management. One important area that defines how well and efficient a fast food restaurant delivers its product and services to customers is by their implementation of the queue management practices at the restaurant and the level of customers satisfaction. A study is conducted to monitor the distribution of queuing time, queue length, customer arrival and departure patterns at a McDonald’s restaurant located in Tampines, Singapore. Thus, the purpose of this study is to propose an online system that will aid in managing queue during the service and hence, to optimize the queuing time. There were few methods involved in order to achieve the objectives, including conducting observation, interview, time study and develop the online booking system. Through this system, it can help to manage queue and improving the customer satisfaction
Comparison of markets for organic food in six EU states.
This report was presented at the UK Organic Research 2002 Conference. Recent research confirms that the decision to convert is now highly influenced by financial incentives arising from EU regulations but the exact mix of incentives depends on prevailing government policies and access to premium markets so that the organic sector in most countries is now referred to as either government-led or market-driven. The objective of the paper is to compare development of the sector along these two polarities but set within the context of "common elements of interest" within new agrifood methodologies: time, space, power, and meaning (Cooke, Uranga and Etxebarria 1998; Morgan and Murdoch 2000). The paper presents preliminary findings relating to six EU States: UK, Ireland, Austria, Denmark, Portugal and Italy, and through the application of "worlds of production" to market outlets and suggests discourses that define these outlets. The analysis aims to inform the further study of farmer marketing decisions and practices
Starburst radio galaxies: general properties, evolutionary histories and triggering
In this paper we discuss the results of a programme of spectral synthesis
modelling of a sample of starburst radio galaxies in the context of scenarios
for the triggering of the activity and the evolution of the host galaxies. The
starburst radio galaxies -- comprising ~15 - 25% of all powerful extragalactic
radio sources -- frequently show disturbed morphologies at optical wavelengths,
and unusual radio structures, although their stellar masses are typical of
radio galaxies as a class. In terms of the characteristic ages of their young
stellar populations (YSP), the objects can be divided into two groups: those
with YSP ages t_ysp < 0.1 Gyr, in which the radio source has been triggered
quasi-simultaneously with the main starburst episode, and those with older YSP
in which the radio source has been triggered or re-triggered a significant
period after the starburst episode. Combining the information on the YSP with
that on the optical morphologies of the host galaxies, we deduce that the
majority of the starburst radio galaxies have been triggered in galaxy mergers
in which at least one of the galaxies is gas rich. However, the triggering (or
re-triggering) of the radio jets can occur immediately before, around, or a
significant period after the final coalescence of the merging nuclei,
reflecting the complex gas infall histories of the merger events. Overall, our
results provide further evidence that powerful radio jet activity can be
triggered via a variety of mechanisms, including different evolutionary stages
of major galaxy mergers; clearly radio-loud AGN activity is not solely
associated with a particular stage of a unique type of gas accretion event.Comment: 16 pages, 3 Figures, accepted for publication in MNRA
Impact of ^(16)O(γ,α)^(12)C measurements on the ^(12)C(α,γ)^(16)O astrophysical reaction rate
The ^(12)C(α,γ)^(16)O reaction, an important component of stellar helium burning, plays a key role in nuclear astrophysics. It has direct impact on the evolution and final state of massive stars, while also influencing the elemental abundances resulting from nucleosynthesis in such stars. Providing a reliable estimate for the energy dependence of this reaction at stellar helium burning temperatures has been a major goal for the field. In this work, we study the role of potential new measurements of the inverse reaction, ^(16)O(γ,α)^(12)C, in reducing the overall uncertainty. A multilevel R-matrix analysis is used to make extrapolations of the astrophysical S factor for this reaction to the stellar energy of 300 keV. The statistical precision of the S-factor extrapolation is determined by performing multiple fits to existing E1and E2 ground-state capture data, including the impact of possible future measurements of the ^(16)O(γ,α)^(12)C reaction. In particular, we consider a proposed Jefferson Laboratory (JLab) experiment that will make use of a high-intensity low-energy bremsstrahlung beam that impinges on an oxygen-rich single-fluid bubble chamber in order to measure the total cross section for the inverse reaction. The importance of low-energy data as well as high-precision data is investigated
Antigen depot is not required for alum adjuvanticity
Alum adjuvants have been in continuous clinical use for more than 80 yr. While the prevailing theory has been that depot formation and the associated slow release of antigen and/or inflammation are responsible for alum enhancement of antigen presentation and subsequent T- and B-cell responses, this has never been formally proven. To examine antigen persistence, we used the chimeric fluorescent protein EαGFP, which allows assessment of antigen presentation in situ, using the Y-Ae antibody. We demonstrate that alum and/or CpG adjuvants induced similar uptake of antigen, and in all cases, GFP signal did not persist beyond 24 h in draining lymph node antigen-presenting cells. Antigen presentation was first detectable on B cells within 6–12 h of antigen administration, followed by conventional dendritic cells (DCs) at 12–24 h, then finally plasmacytoid DCs at 48 h or later. Again, alum and/or CpG adjuvants did not have an effect on the magnitude or sequence of this response; furthermore, they induced similar antigen-specific T-cell activation in vivo. Notably, removal of the injection site and associated alum depot, as early as 2 h after administration, had no appreciable effect on antigen-specific T- and B-cell responses. This study clearly rules out a role for depot formation in alum adjuvant activity
Ena/VASP function in retinal axons is required for terminal arborization but not pathway navigation
The Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family of proteins is required for filopodia formation in growth cones and plays a crucial role in guidance cue-induced remodeling of the actin cytoskeleton. In vivo studies with pharmacological inhibitors of actin polymerization have previously provided evidence for the view that filopodia are needed for growth cone navigation in the developing visual pathway. Here we have re-examined this issue using an alternative strategy to generate growth cones without filopodia in vivo by artificially targeting Xena/XVASP (Xenopus homologs of Ena/VASP) proteins to mitochondria in retinal ganglion cells (RGCs). We used the specific binding of the EVH1 domain of the Ena/VASP family of proteins with the ligand motif FP4 to sequester the protein at the mitochondria surface. RGCs with reduced function of Xena/XVASP proteins extended fewer axons out of the eye and possessed dynamic lamellipodial growth cones missing filopodia that advanced slowly in the optic tract. Surprisingly, despite lacking filopodia, the axons navigated along the optic pathway without obvious guidance errors, indicating that the Xena/XVASP family of proteins and filopodial protrusions are non-essential for pathfinding in retinal axons. However, depletion of Xena/XVASP proteins severely impaired the ability of growth cones to form branches within the optic tectum, suggesting that this protein family, and probably filopodia, plays a key role in establishing terminal arborizations
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