Physical parameters in the hot spots and jets of Compact Symmetric Objects

We present a model to determine the physical parameters of jets and hot spots of a sample of CSOs under very basic assumptions like synchrotron emission and minimum energy conditions. Based on this model we propose a simple evolutionary scenario for these sources assuming that they evolve in ram pressure equilibrium with the external medium and constant jet power. The parameters of our model are constrained from fits of observational data (radio luminosity, hot spot radius and hot spot advance speed) versus projected linear size. From these plots we conclude that CSOs evolve self-similarly and that their radio luminosity increases with linear size along the first kiloparsec. Assuming that the jets feeding CSOs are relativistic from both kinematical and thermodynamical points of view, we use the values of the pressure and particle number density within the hot spots to estimate the fluxes of momentum (thrust), energy, and particles of these relativistic jets. The mean jet power obtained in this way is within an order of magnitude that inferred for FRII sources, which is consistent with CSOs being the possible precursors of large doubles. The inferred flux of particles corresponds to, for a barionic jet, about a 10% of the mass accreted by a black hole of $10^8 {\rm M_{\odot}}$ at the Eddington limit, pointing towards a very efficient conversion of accretion flow into ejection, or to a leptonic composition of jets.Comment: 11 pages, 2 figures. Accepted for publication in Astrophysical Journa

A Search for Molecular Gas in GHz Peaked Spectrum Radio Sources

We present searches for molecular gas (CO, OH, CS, and Ammonia) in six GHz Peaked Spectrum (GPS) radio sources. We do not detect gas in any source and place upper limits on the mass of molecular gas which are generally in the range 1E9 to a few times 1E10 solar masses. These limits are consistent with the following interpretations: (1) GPS sources do not require very dense gas in their hosts, and (2) The GPS sources are unlikely to be confined by dense gas and will evolve to become larger radio sources

Dating COINS: Kinematic Ages for Compact Symmetric Objects

We present multi-epoch VLBA observations of Compact Symmetric Objects (CSOs) from the COINS sample (CSOs Observed In the Northern Sky). These observations allow us to make estimates of, or place limits on, the kinematic ages for those sources with well-identified hot spots. This study significantly increases the number of CSOs with well-determined ages or limits. The age distribution is found to be sharply peaked under 500 years, suggesting that many CSOs die young, or are episodic in nature, and very few survive to evolve into FR II sources like Cygnus A. Jet components are found to have higher velocities than hot spots which is consistent with their movement down cleared channels. We also report on the first detections of significant polarization in two CSOs, J0000+4054 (2.1%) and J1826+1831 (8.8%). In both cases the polarized emission is found in jet components on the stronger side of the center of activity.Comment: 34 pages including 7 figures, Accepted to ApJ on Dec 7, 200

The Role of Fermions in Bubble Nucleation

We present a study of the role of fermions in the decay of metastable states of a scalar field via bubble nucleation. We analyze both one and three-dimensional systems by using a gradient expansion for the calculation of the fermionic determinant. The results of the one-dimensional case are compared to the exact results of previous work.Comment: 15 pages, revtex, 9 figure

An exploratory study: Corporate social responsibility perceptions in Guinea-Bissau and Ivory Coast

Corporate Social Responsibility (CSR) is now crucial to enhance long-term competitiveness. CSR is also linked with several strategic business dimensions such as innovation, performance, and competitive success. However, most of the available studies conducted at the moment use samples from developed countries in America and Europe, and insufficient attention has been given to less developed countries, particularly in Africa. Taking into account that the current models to understand and measure the concept of CSR, and to determine how to obtain competitive advantage through responsible business behaviour, have not yet been applied to Africa, this article is a first step to fill the gap. Based on recently published models addressing the above-mentioned variables, this paper aims to study CRS through the application of a questionnaire to managers in two countries in West Africa: Guinea-Bissau and the Ivory Coast. The main goal of this exploratory study was the understanding of the current situation of CSR managers´ perceptions in both countries. For this purpose, the paper uses an overall scale to examine the different theoretical dimensions reflecting CSR: social, economic, and environmental dimensions. The results show that there is a generally positive perception of the CSR elements, although the emphasis is given to economic issues and the social issues related to human resources, training and empowerment of employees and leadership skills, among others. As conclusion the study points out the role of managers in promoting a culture of social innovation by focusing on the CSR philosophy.info:eu-repo/semantics/publishedVersio

Polarimetry of Compact Symmetric Objects

We present multi-frequency VLBA observations of two polarized Compact Symmetric Objects (CSOs), J0000+4054 and J1826+1831, and a polarized CSO candidate, J1915+6548. Using the wavelength-squared dependence of Faraday rotation, we obtained rotation measures (RMs) of -180 \pm 10 rad m^-2 and 1540 \pm 7 rad m^-2 for the latter two sources. These are lower than what is expected of CSOs (several 1000 rad m^-2) and, depending on the path length of the Faraday screens, require magnetic fields from 0.03 to 6 \mu G. These CSOs may be more heavily affected by Doppler boosting than their unpolarized counterparts, suggesting that a jet-axis orientation more inclined towards the line of sight is necessary to detect any polarization. This allows for low RMs if the polarized components are oriented away from the depolarizing circumnuclear torus. These observations also add a fourth epoch to the proper motion studies of J0000+4054 and J1826+1831, constraining their kinematic age estimates to >610 yrs and 2600 \pm 490 yrs, respectively. The morphology, spectrum, and component motions of J1915+6548 are discussed in light of its new classification as a CSO candidate, and its angle to the line of sight (~50\deg) is determined from relativistic beaming arguments.Comment: 29 pages, including 9 figures; Accepted by Astrophysical Journal, 16 Feb 0

Value co-creation in hospitality industry: A systematic literature review

Service dominant (S-D) logic, which advocates prominence of services rather than goods in economic exchange, has become one of most the popular research streams in recent years. One of the most prominent theories of (S-D) logic is value co-creation. Although co-creation is mutually beneficial, it is considered to be customer-oriented and interactional. In a dynamic and interactive industry like the hotel industry, the creation of value through interaction and engagement with customers is significant to enhance business performance. This article reports a systematic literature review (SLR) to critically analyse the key findings of the publications in the domain of value co-creation related to the hospitality industry. This article also endeavours to identify and critically analyse the key themes, theories, and constructs of prior studies. The findings show that the interactive co-creative experience is significant to create positive emotion and satisfaction for hotel guests. This positive emotion and satisfaction encourage the guests to come back to the hotel and recommend it to others. Interactional co-creation also leads to more engagement, which has been found to have a significant effect on hotel performance. Therefore, hotel management should invest time and money to train and encourage hotel employees to accelerate interaction and engagement with guests to create better experience for hotel guests. This should enhance hotel performance.info:eu-repo/semantics/publishedVersio

Improved semiclassical density matrix: taming caustics

We present a simple method to deal with caustics in the semiclassical approximation to the thermal density matrix of a particle moving on the line. For simplicity, only its diagonal elements are considered. The only ingredient we require is the knowledge of the extrema of the Euclidean action. The procedure makes use of complex trajectories, and is applied to the quartic double-well potential.Comment: 20 pages, 7 figures. Revised version, accepted for publication in Phys. Rev.

Consórcio de girassol com mandioca na ecorregião dos Tabuleiros Costeiros.

O objetivo deste trabalho foi conhecer a produtividade de cultivares de girassol quando cultivadas em monocultivo e em consórcio com mandioca na ecorregião dos Tabuleiros Costeiros do Nordeste. Foi Instalado um experimento com 20 cultivares de girassol e com a variedade de mandioca BRS Kiriris. Foi avaliado o peso dos aquênios para estabelecer o rendimento de grãos de cada cultivar de girassol nos sistemas de consórcio e monocultivo. Foram verificadas diferenças significativas entre as cultivares avaliadas, evidenciando diferenças genéticas entre elas em ambos os sistemas de plantio. Na média, os rendimentos de grãos de girassol foram de 1.432 kg/ha, em monocultivo e 1.467 kg/ha, em consórcio com mandioca. Algumas cultivares de girassol, como a NTO 2.0, produziram mais em monocultivo (1.869 kg/ha) que no sistema consorciado (1.519 kg/ha). Outras, como a Aguará 6, produziram mais no sistema consorciado (1.816 kg/ha) que em monocultivo (1.504 kg/ha). O sistema de plantio em consórcio do girassol com mandioca BRS Kiriris foi favorável superando ou mantendo próximo à produtividade do sistema de monocultivo. A média geral de rendimento de grãos de girassol, na média dos sistemas de plantio adotados, foi de 1.450 kg/ha, atestando o potencial produtivo do conjunto de girassóis avaliado. As cultivares NTO 2.0, AGUARÁ 6 , NTO 3 .0, BRS G 26, PARAISO 33, M 734, BRS 322, OLISUN, HELIO 253 e AGUARÁ 4, citadas pela ordem decrescente de produtividade e com rendimentos médios de grãos acima da média geral, podem ser indicadas para cultivo na ecorregião dos Tabuleiros Costeiros em monocultivo e em consórcio com mandioca. INTERCROPPING OF SUNFLOWER WITH CASSAVA IN THE COASTAL TABLELAND ECOREGION OF BRAZIL. The objective of this study was to determine the productivity of sunflower cultivars monoculture and intercropped with cassava in the Coastal Tableland eco-region of Brazil. The experiment was conducted with 20 cultivars of sunflower and a variety of cassava BRS Kiriris. The weight of grains was evaluated to establish the yield of each cultivar of sunflower in the intercropping and monoculture systems. There were significant differences between cultivars, indicating genetic differences between them in both tillage systems. On average, the grain yields of sunflower were 1,432 kg ha in monoculture and 1,467 kg/ha in intercropped with cassava. Some sunflower cultivars, such as NTO 2.0, produced more in monoculture (1,869 kg/ha) than in the intercropping system (1,519 kg/ha). Others, such as Aguará 6 produced more in intercropping system (1,816 kg/ha) than in monoculture (1,504 kg/ha). The planting of sunflower in intercropping system with cassava BRS Kiriris was favorable, surpassing the productivity of the monoculture system. The average yield of sunflower grain in the mean of the cropping systems adopted was of 1,450 kg/ha, attesting to the productive potential of the sunflowers evaluated. The Cultivars NTO 2.0, Aguará 6, NTO 3.0, BRS G 26, PARAISO 33, M 734, BRS 322, OLISUN, HELIO 253 and Aguará 4, cited in the order of decreasing productivity can be indicated for cultivation in the Tableland eco-region of Brazil in monoculture and intercropped with cassava

On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes' electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern gamma-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.Comment: 32 pages, 3 figures included. Revised version, accepted for publication in Ap