Little is known about the amount and form of mercury released from inoperative mercury mines in the western United States. To address this, we measured mercury concentrations and speciation in water ...impacted by the New Idria mine. Total unfiltered mercury concentrations (UHgT) in acid mine drainage (AMD) (5.2 to 41 ng/L) were comparable to concentrations upstream from the mine (4.2 to 13 ng/L). We measured substantially higher UHgT concentrations (2900 to 12 400 ng/L) in water 1.2 km downstream from the AMD input and estimate that the creek transports a baseline flux of 1.5 kg of Hg/yr from the mine site. We hypothesize that tailings are the primary source of mercury to this creek. We attribute the decrease in UHgT along a downstream transect to Hg(II) scavenging by iron oxyhydroxide particles that precipitate and settle out of the water. Likewise, dissolved gaseous mercury concentrations decreased with increasing distance from the mine (2.8 ng/L at 1.2 km; 0.56 ng/L at 7.5 km). We regard abiotic atmospheric evasion as the primary mechanism driving this loss. The released mercury is biologically available, evidenced by high (1.1 to 1.7 ng/L) unfiltered monomethylmercury concentrations downstream from the mine. We attribute the relatively uniform downstream monomethylmercury concentrations to a balance between microbial methylation and demethylation.
An investigation of war‐trauma was made utilizing an initial pool of 1,268 undergraduates at the American University of Beirut. Based on the number of war events the students had experienced, 400 ...students were invited to return for further questioning about their present stress characteristics. Inventories measuring anxiety, depression, and PTSD were administered to 273 students responding to the request. Those who experienced many war events scored significantly higher on all three stress scales. Women scored higher than men on anxiety regardless of war exposure category, but there was no difference between women and men on PTSD or depression.
Computer anxiety was investigated among 308 teachers in Lebanese schools known to use computers in their regular educational programs using the Computer Anxiety Rating Scale. The scale's performance ...is discussed in light of the findings of other studies that used the same scale in international settings. Tendencies in teachers' anxiety are discussed in relation to teachers' educational attributes and their computer background.
Distributed parameter modeling may offer a viable alternative to the finite-element approach for modeling large flexible space structures. In addition, the introduction of the transfer matrix method ...to the continuum modeling process provides a very useful tool to facilitate the distributed parameter model applied to more complex configurations. This paper proposes a piecewise continuous Timoshenko beam model, which was used for the dynamic analysis of a tapered beam-like structure. Instead of the arbitrarily assumed shape functions used in a finite-element analysis, the closed-form solution of the Timoshenko beam equation was used. Application of the transfer matrix method was used to relate all elements as a whole. Using the corresponding boundary conditions and compatibility equations, a characteristic equation for the global tapered beam was produced and natural frequencies derived. The results from this analysis were compared to those obtained from a conventional finite-element analysis. While comparable results are obtained, the piecewise continuous Timoshenko beam model significantly decreased the number of modal elements required.
Dynamic Analysis of Truss-Beam System Abu-Saba, Elias G; McGinley, William M; Montgomery, Raymond C
Journal of aerospace engineering,
10/1991, Letnik:
4, Številka:
4
Journal Article
Recenzirano
As the manned exploration of space continues, many complex structural components are being developed to construct the orbital platforms that will be used to house communication hardware, personnel, ...and manufacturing complexes. These components are extremely flexible and complex in their behavior. There is a need for a simple method for determining the dynamic characteristics of these space structures with a minimum of effort. A mathematical model of one of these structural elements, an articulating truss beam, has been developed to predict its dynamic response. Assumptions of the force interaction between the beam elements and the joints have been made for using this model. Algorithms are provided to determine the flexibility matrix of the truss beam for use in the equation of motion. The natural frequencies obtained from using this method are compared with those obtained by the finite element method. An experimental procedure is planned to validate the results from the theoretical method.
Little is known about the amount and form of mercury released from inoperative mercury mines in the western United States. To address this, we measured mercury concentrations and speciation in water ...impacted by the New Idria mine. Total unfiltered mercury concentrations (UHg sub(T)) in acid mine drainage (AMD) (5.2 to 41 ng/L) were comparable to concentrations upstream from the mine (4.2 to 13 ng/L). We measured substantially higher UHg sub(T) concentrations (2900 to 12 400 ng/L) in water 1.2 km downstream from the AMD input and estimate that the creek transports a baseline flux of 1.5 kg of Hg/yr from the mine site. We hypothesize that tailings are the primary source of mercury to this creek. We attribute the decrease in UHg sub(T) along a downstream transect to Hg(II)scavenging by iron oxyhydroxide particles that precipitate and settle out of the water. Likewise, dissolved gaseous mercury concentrations decreased with increasing distance from the mine (2.8 ng/L at 1.2 km; 0.56 ng/L at 7.5 km). We regard abiotic atmospheric evasion as the primary mechanism driving this loss. The released mercury is biologically available, evidenced by high (1.1 to 1.7 ng/L) unfiltered monomethylmercury concentrations downstream from the mine. We attribute the relatively uniform downstream monomethylmercury concentrations to a balance between microbial methylation and demethylation.
The Female Juvenile Delinquent Abu-Saba, Mary Bentley
Transactional analysis journal,
19/1/1/, Letnik:
5, Številka:
1
Journal Article
Recenzirano
3, Eldefonso, Edward, Law Enforcement and the Youthful Offender, John Wiley and Sons, New York, 1973. 5, The Challenge of Crime in a Free Society, Report by the President's Commission on Law ...Enforcement and Administration of Justice, 1967.
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