873 research outputs found
Spin-String Interaction in QCD Strings
I consider the question of the interaction between a QCD string and the spin
of a quark or an antiquark on whose worldline the string terminates. The
problem is analysed from the point of view of a string representation for the
expectation value of a Wilson loop for a spin-half particle. A string
representation of the super Wilson loop is obtained starting from an effective
string representation of a Wilson Loop. The action obtained in this manner is
invariant under a worldline supersymmetry and has a boundary term which
contains the spin-string interaction. For rectangular loops the spin-string
interaction vanishes and there is no spin-spin term in the resulting heavy
quark potential. On the other hand if an allowance is made for the finite
intrinsic thickness of the flux-tube, by assuming that the spin-string
interaction takes place not just at the boundary of the string world-sheet but
extends to a distance of the order of the intrinsic thickness of the flux tube,
then we do obtain a spin-spin interaction which falls as the fifth power of the
distance. Such a term was previously suggested by Kogut and Parisi in the
context of a flux-tube model of confinement.Comment: 19 pages, 1 figure; Published version with added discussion and
references in section
Effects of Nitrogen Photoabsorption Cross Section Resolution on Minor Species Vertical Profiles in Titan's Upper Atmosphere
The significant variations in both measured and modeled densities of minor species in Titan's atmosphere call for the evaluation of possible influencing factors in photochemical modeling. The effect of nitrogen photoabsorption cross section selection on the modeled vertical profiles of minor species is analyzed here, with particular focus on C2H6 and HCN. Our results show a clear impact of cross sections used on all neutral and ion species studied. Affected species include neutrals and ions that are not primary photochemical products, including species that do not even contain nitrogen. The results indicate that photochemical models that employ low-resolution cross sections may significantly miscalculate the vertical profiles of minor species. Such differences are expected to have important implications for Titan's overall atmospheric structure and chemistry.NASA Outer Planet Research program NNH12ZDA001NInstitute for Computational Engineering and Sciences (ICES
Demographic Characteristics and Frequency of Use among Current Users of Classic Hallucinogens
Little is known about the demographic characteristics of classic hallucinogen users and few investigations address the frequency of their use. This study used five years of data from The National Survey on Drug Use and Health, an annual, nationally representative, cross-sectional survey, conducted by the Substance Abuse and Mental Health Services Administration of the United States government, to examine age, gender, marital status, race/ethnicity, income, education, employment status and health status and among low, medium, and high frequency users of classic hallucinogens (N = 1323). Results indicated classic hallucinogen users were most likely to be White males between 18 and 25 years old, who had never been married, had some college, were employed full-time, had a family income less than $20,000 per year, and were in very good health. High frequency hallucinogen users were more likely to be males in the “Other†racial/ethnic category who were less well educated, and less healthy, but they did not differ from other users in age, marital status, family income, or employment. Limitations and suggestions for future research are discussed
The Phase Diagram of the Sigma Model
We study the phase diagram of the scalar model in
dimensions. We find that the phase transition is of first order in most of the
parameter space. The theory can still be relevant to continuum physics (as an
effective theory) provided the transition is sufficiently weakly first order.
This places restrictions on the allowed coupling constants.Comment: 3 pages (Latex), 2 eps figures, uses espcrc2.sty, epsf, talk given at
LATTICE9
Assessment of Heavy Metals Uptake by Vegetables Cultivated on Soil Receiving Industrial Wastewater in Minna, Nigeria
Consumption of vegetable crops grown on soil irrigated with industrial wastewater has been the order of the day in most urban towns and cities of Nigeria, despite reports of its serious health impact. This study assessed the possibility of uptake of heavy metals by crops grown on soil receiving industrial wastewater during rainy and dry seasons. The crops investigated are Spinach, Cayenne Pepper, Jute mallow, roselle and lady’s fingers okra. The initial composition of the wastewater was analyzed to contain 0.89 mg/l of chromium, 0.74 mg/l of cadmium, 1.04 mg/l of copper and 2.81 mg/l of iron. Control water used for this experiment contain no trace of any of these heavy metals. The experimental soil was also analyzed and contained 0.10 mg/kg of chromium, 0.06 mg/kg of iron before irrigation in dry season. After irrigation at the wastewater plots, the heavy metal concentrations in soil had increased to 6.24 mg/kg of chromium and 7.50 mg/kg of iron. In wet season, the concentrations of heavy metals in the soil were 0.00 mg/kg of chromium and 2.32 mg/kg of iron before irrigation. After irrigation in wet season, the concentrations increased to 6.01 mg/kg of iron. Mean difference of heavy metal concentrations were significantly high in vegetables in dry season, with values ranging from 0.03 mg/kg to 211mg/kg in wastewater plots, 0.20 mg/kg to 215 mg/kg in wet seasons wastewater plots, 0.00 mg/kg to 157 mg/kg in dry season. It is however recommended that consumption of vegetables irrigated with domestic/industrial wastewater be strongly discouraged because of its serious health implications. 
Health Risks Associated with Consumption of Vegetables Grown using Domestic Wastewater in Minna, Niger State, Nigeria
Most vegetables consumed in the cities of developing countries are grown using wastewater discharged through township drainage network. This paper, therefore, investigates the risk involved in the consumption of such vegetables. The human daily intake rate (DIR) and Health Risk Index (HRI) of heavy metals were calculated using established formulae and the values of DIR ranged from 0.10 mg/kg/day to 0.71 mg/kg/day in wastewater plots in dry season for adults and 0.10 mg/kg/day to 0.14 mg/kg/day for children. Health risk index (HRI) values ranges from 0.40 mg/kg/day to 0.75 mg/kg/day in wastewater plots for adults in dry season and 0.20 mg/kg/day to 0.95 mg/kg/day for children. In wet season wastewater plots, the HRI ranges from 0.40 mg/kg/day to 0.95 mg/kg/day for children. The values of Hazard index (HI) ranged between 1.00 mg/kg/day and 1.21 mg/kg/day for all the seasons. Statistical analysis showed that there is a significant difference between the wet and dry season values for all the parameters assessed. Finally, uptake of heavy metals from the soil by all the vegetable crops under investigation was established. Therefore proper monitoring needs to be carried out to regulate consumption of vegetables produced from the experimental sites as continuous application of the industrial wastewater may lead to further accumulation of these heavy metals
Effects of a Policy Development Process on Implementing an Equity-Based Policy
Unstable residential and inadequate academic environments lead to poor educational outcomes for low-income students in urban areas. In 2011, Ohio enacted a law to create a college preparatory boarding school (CPBS) for low-income students by 2013. However, Ohio\u27s CPBS has not yet been established, thereby denying these students an opportunity to attain skills needed to enter college. Using the policy feedback theory (PFT) and Fredrickson\u27s theory of social equity (SET) as foundations, the purpose of this qualitative study was to understand the nature of implementation barriers and propose solutions by exploring 2 successful CPBS programs in Maryland and Washington, D.C. The research questions focused on identifying implementation practices from the successful CPBS programs with the aim to propose options to implement Ohio\u27s law. Data were collected from a purposeful sample of 14 participants which included 2 Ohio legislators; public administrators, Ohio (7), Maryland (1), Washington, D.C (3); and 1 Ohio union leader, and a review of relevant public and official records. All data were deductively coded and subjected to a constant comparison analysis. Results showed that Ohio\u27s public education administrators were excluded from the CPBS policy\u27s design, unlike their peers. Further, Ohio\u27s CPBS law favored a particular stakeholder involved in its design and was not executed when Ohio\u27s education administrators and the entity disagreed over public assets ownership. The findings affirmed SET\u27s condition for an open and inclusive policy process and PFT\u27s claim that current policies affect resources and the paradigm for new policies. Positive social change implications from this study include recommendations to Ohio\u27s policymakers to create a more inclusive process involving parties willing to provide an effective learning environment for economically marginalized children
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