Effects of torsion on the behavior of peripheral steel‐braced frame systems

In this study, the torsional response of buildings with peripheral steel‐braced frame lateral systems is evaluated. A three‐dimensional model of a three story braced frame with various levels of eccentricity is created and the effects of torsion on the seismic response is assessed for four hazard levels. The response history analysis results indicate that, unlike frame structures, the torsional amplifications in the inelastic systems exceed those of corresponding elastic systems and tend to increase with an increase in the level of inelasticity. The ability of two simplified procedures, elastic response spectrum analysis and pushover analysis, to capture the torsional amplifications in steel‐braced frames is evaluated. Copyright © 2010 John Wiley & Sons, Ltd.     

Delineating volcanic aquifer recharge areas using geochemical and isotopic tools

Relative recharge areas are evaluated using geochemical and isotopic tools, and inverse modeling. Geochemistry and water quality in springs discharging from a volcanic aquifer system in Guatemala are related to relative recharge area elevations and land use. Plagioclase feldspar and olivine react with volcanically derived CO₂ to produce Ca-montmorillonite, chalcedony and goethite in the groundwater. Alkalinity, Mg, Ca, Na, and SiO_2(aq) are produced, along with minor increases in Cl and SO₄ concentrations. Variations in groundwater δD and δ¹⁸O values are attributed to recharge elevation and used in concert with geochemical evolution to distinguish local, intermediate, and regional flow systems. Springs with geochemically inferred short flow paths provided useful proxies to estimate an isotopic gradient for precipitation (??.67 δ¹⁸O/100?m). No correlation between spring discharge and relative flow-path length or interpreted recharge elevation was observed. The conceptual model was consistent with evidence of anthropogenic impacts (sewage and manure) in springs recharged in the lower watershed where livestock and humans reside. Spring sampling is a low-budget approach that can be used to develop a useful conceptual model of the relative scale of groundwater flow (and appropriate watershed protection areas), particularly in volcanic terrain where wells and boreholes are scarce.     

The Bioavailability of Effluent-derived Organic Nitrogen along an Estuarine Salinity Gradient

Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first 2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient.     

Platinum-group elements in the Merensky reef. I. PGE in solid solution in base metal sulfides and the down-temperature equilibration history of Merensky ores

 The platinum-group elements (PGE) in base metal sulfides (BMS) of the Merensky reef are mostly close to the detection limit of the proton microprobe. The only phase that accommodates appreciable PGE is pentlandite. Total average PGE plus Au grades of the sulfide fraction of the Merensky reef are about 500 ppm. We estimate the modal proportions of the major BMS to be around 53 percent pyrrhotite, 25 percent pentlandite, and 22 percent chalcopyrite (ignoring minor phases). Using this estimate, we calculate by how much the sulfides are oversaturated with respect to individual PGE. With respect to Pt, the sulfides are many times oversaturated, i.e., nearly all Pt occurs as discrete PGE phases. With regard to Pd the sulfides are oversaturated by about a factor of two. The Ru and Rh levels are at and below saturation levels. Available experiments suggest that the entire PGE content of the sulfide fraction can easily be accommodated in solid solution in BMS at temperatures as low as 500°C. The fact that the BMS are oversaturated with most PGE thus indicates that the sulfides have continued to exsolve PGE below that temperature. Calculated sulfur fugacities indicate that f _S2 is controlled by silica activity, as expected in high-temperature ores, suggesting that metal/sulfur ratios of the ore may not have changed much since complete solidification of the intercumulus silicate melt of the Merensky reef. All sulfides investigated have cooled below the maximum temperature of pentlandite-pyrite coexistence, which experiments place at 250±30°C. Final closure temperatures of the sulfide-PGE mineral assemblages, approximated by extrapolating the pentlandite-pyrrhotite solvus beyond its experimentally determined range, are possibly as low as 80 to 90°C. Received: 25 April 1995/Accepted: 5 September 1995     

The impact of moral conditions associated with culture on the traditional adoption-diffusion Model: The case of the Qassim Region of Saudi Arabia

The main objective of this paper is to develop a conceptual framework that views cooperative membership in Saudi Arabia as a function of both utilitarian and deontological (moral) perspectives. The research was conducted in the Qassim, an agricultural area located in the Central Region of Saudi Arabia. The sample includes 83 cooperative members, besides 136 non-members. Discriminant analysis is used to test the hypothesis derived in this research. Two models are examined, the first model is based on the traditional adoption-diffusion framework. Thus, discriminating variables included in the first model are related to the socioeconomic characteristics of respondents, information content, sources of information, and advantages of membership in agricultural cooperatives. In the second model, discriminating variables pertaining to moral conditions were used in addition to the original discriminating variables. Results of the discriminant analysis fit the theoretical framework of the study, meaning that farmers become members because of economic (utilitarian) expectations and also because of their desire to cooperate with other farmers. Deontology therefore plays an important role in distinguishing members from non-members.     

Variations in trapping temperatures and trace elements in peridotite-suite inclusions from African diamonds: evidence for two inclusion suites,and implications for lithosphere stratigraphy

The proton microprobe has been used to measure the trace element contents of Cr-pyrope, olivine and orthopyroxene inclusion (DI) in>60 diamonds from southern Africa, and in concentrate garnets from the host kimberlites. Olivine inclusions show a negative correlation of Ca with Fo content, but olivines coexisting with very subcalcic garnets are anomously depleted in Ca relative to Fo. The maximum and median values of Ti, Zn, Ga, Zr and Y in DI garnets decrease as Ca decreases relative to Cr, consistent with increasing depletion by removal of silicate melts. However, the most subcalcic garnets are anomously enriched in Sr (and LREE). The contrasting depletion in Zr, Y, Ti etc. and enrichment in Sr is not consistent with a single-stage depletion event. The extreme Ca depletion of the most subcalcic garnets and their coexisting olivines, and the Sr enrichment, are interpreted as the result of metasomatism by a carbonatitic fluid following depletion. Trapping temperatures of garnet DI, estimated by nickel thermometry range from 950 to > 1500°C. Most DI with T>1200°C are lherzolitic, rather than subcalcic. In most pipes studied, the trapping T of DI garnets is higher than the T range of equivalent garnets from concentrates. The high Ts are interpreted as reflecting the formation of diamonds during short-lived thermal pulses, followed by cooling toward a conductive geotherm. The T distribution of calcic and subcalcic garnets in concentrates from kimberlites suggests that lherzolite and harzburgite are intimately intermixed over the depth range 150–180 km beneath the Kalahari craton. The abundance of calcic garnets with T>1200°C suggests the presence of significant amounts of lherzolite at greater depths. This deeper lherzolite may be associated with eclogite, and may be the source region for some high-T lherzolitic DI garnets.     

Be isotope and B-Be investigations of the historic eruptions of Mt. Vesuvius

Cosmogenic and radioactive ¹⁰Be, stable ⁹Be and B concentrations have been determined for four alkaline lavas from the recent cycle of historical activity at Mt. Vesuvius, in the Central Campania Province (Italy). The goal of this study was to use the Be isotope and Be-B systematics of these lavas in a manner analogous to that used in regions unequivocally related to active subduction, in hopes of being able to document a subduction origin for the Vesuvian lavas. Four lavas measured to date have low ¹⁰Be concentrations as well as low B/Be ratios. While the low ¹⁰Be concentrations could reflect subduction and incorporation of old sediments and/or only contributions from the basaltic part of the subducting plate, the combination of low ¹⁰Be and low B/Be ratios must be interpreted as the absence of a subduction signature in these lavas. Unfortunately, the absence of a subduction signature in the lavas cannot be used unequivocally to argue against recent subduction in the Central Campania region. Subduction of an unusually young, hot slab which has lost its B through prograde metamorphic reactions at shallow levels could explain the absence of a subduction signature, as could extensive crustal contamination. In addition, recent studies in Java show that alkaline lavas in this region of active subduction never show a subduction signature, even when erupting in close proximity to calc-alkaline and tholeiitic lavas which do; by analogy, the Vesuvian lavas studied may have been generated in a part of the sub-arc mantle which either does not experience or does not preserve the chemical signature of subduction modification. The present data set does not allow us to make definitive statements about the role of subduction in the origin of the Central Campania lavas.     

Interpretation of metal concentrations in estuarine sediments of Florida using aluminum as a reference element

Metal contamination of estuarine sediments is an increasing problem in Florida and elsewhere as urbanization extends into previously undeveloped areas. Effective estuarine management practices require scientifically valid tools to assess the extent of estuarine contamination. Interpretation of anthropogenic metal contributions has been hampered by the fact that natural metal concentrations in sediments vary by orders of magnitude in different sediments. Normalization of metal concentrations to a reference element, aluminum, appears to be a promising method for comparing estuarine sediment metal concentrations on a regional basis. In this paper we describe an interpretive method based on the relationship between sediment metals and aluminum derived from statewide data on natural estuarine sediments in Florida. We show how the method can be used to interpret metal concentrations with an example using data from the Miami River and Biscayne Bay.