A Magnetic Dynamo Origin For The Sub-mm Excess In Sgr A*

The sub-mm bump observed in the spectrum of Sgr A* appears to indicate the existence of a compact emitting component within several Schwarzschild radii, $r_S$, of the nucleus at the Galactic Center. This is interesting in view of the predicted circularized flow within $\sim 5-10 r_S$, based on detailed multi-dimensional hydrodynamic simulations of Bondi-Hoyle accretion onto this unusual object. In this paper, we examine the physics of magnetic field generation by a Keplerian dynamo subject to the conditions pertaining to Sgr A*, and show that the sub-mm bump can be produced by thermal synchrotron emission in this inner region. This spectral feature may therefore be taken as indirect evidence for the existence of this circularization. In addition, the self-Comptonization of the sub-mm bump appears to produce an X-ray flux exceeding that due to bremsstrahlung from this region, which may account for the X-ray counterpart to Sgr A* discovered recently by {\it Chandra}. However, the required accretion rate in the Keplerian flow is orders of magnitude smaller than that predicted by the Bondi-Hoyle simulations. We speculate that rapid evaporation, in the form of a wind, may ensue from the heating associated with turbulent mixing of gas elements with large eccentricity as they settle down into a more or less circular (i.e., low eccentricity) trajectory. The spectrum of Sgr A* longward of $\sim 1-2$ mm may be generated outside of the Keplerian flow, where the gas is making a transition from a quasi-spherical infall into a circularized pattern.Comment: 40 pages, 9 figure

Polarized mm And sub-mm Emission From Sgr A* At The Galactic Center

The recent detection of significant linear polarization at mm and sub-mm wavelengths in the spectrum of Sgr A* (if confirmed) will be a useful probe of the conditions within several Schwarzschild radii ($r_S$) of the event horizon at the Galactic Center. Hydrodynamic simulations of gas flowing in the vicinity of this object suggest that the infalling gas circularizes when it approaches within $5-25 r_S$ of the black hole. We suggest that the sub-mm ``excess'' of emission seen in the spectrum of Sgr A* may be associated with radiation produced within the inner Keplerian region and that the observed polarization characteristics provide direct evidence for this phenomenon. The overall spectrum from this region, including the high-energy component due to bremsstrahlung and inverse Compton scattering processes, is at or below the recent {\it Chandra} measurement, and may account for the X-ray source if it turns out to be the actual counterpart to Sgr A*.Comment: 12 pages, 2 figures. published in APJ Letter

Challenges of urban housing quality and its associations with neighbourhood environments: Insights and exepriences of Ibadan City, Nigeria

A survey of housing quality and neighbourhood environments of Ibadan City, Nigeria was conducted to evaluate the housing infrastructure and to identify those areas where there is a likelihood of future incidences of disease and epidemics. Based on existing demographic and land use characteristics, the city can be divided into high, medium and low-density zones. Penalty scoring, rather than positive scoring, was used to assess the conditions and quality of houses and the neighbourhood environment in each of the zones.Houses in the high-density area have the worst property and environmental characteristics followed by houses in the medium-density area. Based on housing condition alone, approximately half of all the dwellings surveyed (n = 172) in the three zones are categorised as either substandard or unfit for human habitation. Based on neighbourhood environment, none of the high and medium-density housing areas and only one of the low density areas attained the good-scoring grade. This is attributed in part to many residents being polygamists which means the houses are overcrowded with perhaps up to eight persons per room and to tenant abuse by internal conversion to increase the occupancy rate. More than half of the houses surveyed have at least or more major defect.Recommendations include government directed infrastructure improvements; a regeneration-drive by private investors with possible displacement of residents fromthe high-density zone to new towns; a vigorous programme of housing and health education; enhanced collaboration between stakeholders to develop enforceable standards for existing housing stock and future builds

Depression amongst healthcare workers in Maiduguri, north-eastern Nigeria

Objective: Very few studies reported the high prevalence of emotional reactions amongst healthcare workers, in sub-Saharan Africa. This study aimed to assess the prevalence of depression among health care workers in two tertiary health institutions in Maiduguri, north-Eastern Nigeria.Methods: In this comparative, cross-sectional study, we used a stratified sampling technique to recruit 370 healthcare workers (clinical and non-clinical staff) from university teaching hospital, and Federal Neuro-psychiatric Hospital, Maiduguri, Borno State, north-east Nigeria. The participants completed a semi-structured socio-demographic questionnaire and Beck Depression Inventory (BDI-II).Results: Twenty (10.7%) and 14 (7.6%) clinical and non-clinical health care workers, respectively had depression (÷2 = 1.096, df = 1, ñ = 0.295). The prevalence of depression in males and females were 7.8% and 26.9%, respectively. Gender had a significant association with depression (÷2 = 3.427, df = 1, ñ =0.043).Conclusion: For an effective healthcare delivery service, the psychological well-being of hospital workers must be improved. Hospital workers require skills on stress management techniques.Keywords: Depression, healthcare workers, Maiduguri, Nigeri

Adoption of Good Agronomic Practices (GAP) Among Smallholder Rice Farmers in Nigeria Agricultural Transformation Agenda

This study assessed the adoption rate and identified factors influencing adoption of rice technologies among participants of Agricultural Transformation Agenda across the targeted implementation zones of Adani-Omor, Bida-Badeggi, Kano-Jigawa and Kebbi-Sokoto. Multi-stage sampling procedure was used in selecting eighty respondents for the study. The data were collected with the aid of structured questionnaire. Descriptive statistics and Tobit regression model were employed in the analysis of data. The study revealed that majority of farmers participating in Agricultural Transformation Agenda Project (ATASP-1) are youths and still in their active age as indicated by the average age of 42 years. About 62% have secondary and tertiary education. On the gender distribution of the people engaged in ATASP-1 project, it was revealed that about 92% were male while only 8% were female. Substantial numbers of technologies were disseminated on rice being promoted under ATASP-1 project and the adoption rate of these technologies was very high. More than three-quarter of the respondents have adopted technologies introduced to them. Adoption of rice technologies among participating farmers is largely depends on socioeconomic characteristics of farmers such as age, education and gender of the respondents. The study recommends that there should be continuous training of farmers on the importance of these technologies as well as techniques behind their utilization to ensure continuous usage of the adopted technologies. Women should be encouraged to participate more in the project and to take up farming as a business. Also, adequate attention should be given to farmers socioeconomic characteristics as these are the determinants of technology adoption. Keywords: Adoption, GAP, Rice Farmers, Agricultural Transformation Agenda DOI: 10.7176/JESD/10-15-02 Publication date: August 31st 201

Measurement of Technical Efficiency of Irrigated and Rainfed Onion Farms in Kano State of Nigeria

This study estimated technical efficiency of irrigated and rain-fed onion production in Kano State of Nigeria, and was carried out in six selected Local Government Areas (LGAs) of the state. A multi-stage sampling technique was used to select 217 onion farmers involved in both irrigated and Rain-fed production systems. The study made use of primary data, collected through structured questionnaires. Descriptive statistics and stochastic frontier model were used to analyse the data. Generally, young literate married men with 5 household size and14 years of farming experience were involved in onion farming. The Maximum Likelihood Estimate (MLE) for production frontier shows that the variable inputs (farm size, hired and family labour, seeds and fertilizers) have positive coefficients and were significant at 5% level. This implied positive effect on onion yields under both production systems, while agro-chemical was negative under rain-fed. The mean technical efficiency was higher for irrigated onion farmers than rain-fed farmers indicating that onion production was technically more efficient under irrigation system of production than rain-fed system of production. Educations, experience, membership of cooperative, access to credit are socio-economic variables that reduce technical inefficiency in both systems of production. The following recommendations were made; contract farming, introduction of hybrid seeds, formation of cooperative societies and private partnership participation with government should be encouraged to boost irrigated onion production not only for home and local industry but also for export to other countries of the world. Keywords: Technical efficiency, irrigated, rain-fed, onion production DOI: 10.7176/JRDM/54-02 Publication date: April 30th 201

On the Propagation of Slip Fronts at Frictional Interfaces

The dynamic initiation of sliding at planar interfaces between deformable and rigid solids is studied with particular focus on the speed of the slip front. Recent experimental results showed a close relation between this speed and the local ratio of shear to normal stress measured before slip occurs (static stress ratio). Using a two-dimensional finite element model, we demonstrate, however, that fronts propagating in different directions do not have the same dynamics under similar stress conditions. A lack of correlation is also observed between accelerating and decelerating slip fronts. These effects cannot be entirely associated with static local stresses but call for a dynamic description. Considering a dynamic stress ratio (measured in front of the slip tip) instead of a static one reduces the above-mentioned inconsistencies. However, the effects of the direction and acceleration are still present. To overcome this we propose an energetic criterion that uniquely associates, independently on the direction of propagation and its acceleration, the slip front velocity with the relative rise of the energy density at the slip tip.Comment: 15 pages, 6 figure