On the Issue of Incomplete and Missing Water-Quality Data in Mine Site Databases: Comparing Three Imputation Methods

Large water-quality databases are valuable for predicting mine drainage chemistry, identifying optimal measures for mitigation and remediation, and refuting/refining models and theories. However, such databases often have missing values due to periodic lack of sampling and analysis or input errors. These missing values lead to problems in machine learning and statistical analysis of water-quality data from mine sites. Using water-quality data collected from 1971 to 1994 from many locations at a copper-molybdenum-gold-silver-rhenium mine site, we compared three imputation methods to estimate missing water-quality data: iterative robust model-based imputation (IRMI), multiple imputations of incomplete multivariate data (AMELIA), and sequential imputation for missing values (IMPSEQ). These methods were evaluated based on mean absolute error, relative absolute error, and percent bias techniques. The results showed that IMPSEQ and IRMI are suitable to impute missing values in water-quality databases at mine sites, whereas AMELIA is not.     

Synthesis,Characterization, and Spectroscopic Analysis of NdxY1−xTiNbO6 Microwave Ceramics

Solid solutions of Nd_xY_1−xTiNbO₆ ceramics were prepared through the solid-state ceramic route. The materials were calcined at 1250°C and sintered in the range 1400–1550°C. The structure of the system was analyzed using the X-ray diffraction and vibrational spectroscopic analysis. The morphology and the sintering behavior of the samples were analyzed using scanning electron microscopy. The dielectric constant (ɛ_r), temperature coefficient of resonant frequency (τ_f), and the unloaded quality factor (Q_u) were measured in the microwave frequency region using the cavity resonator method. The ɛ_r and τ_f increased with an increase in the concentration of Nd in the solid solutions. Nearly zero temperature coefficient of resonant frequency was obtained for the Nd_0.6Y_0.4TiNbO₆ ceramic. Samples are of high quality factor and are useful for microwave applications.     

Accumulation and depuration of polychlorinated biphenyls from field-collected sediment in three freshwater organisms

As laboratory-based bioaccumulation methods are standardized and expanded to include other test species, kinetic studies assessing the major classes of contaminants with these species are needed to adequately select the standard duration for bioaccumulation tests. In the present study we measured the uptake (28-d exposure) of polychlorinated biphenyls (PCBs; total and selected congeners) from field-contaminated sediment in the oligochaete Lumbriculus variegatus, mayfly nymph Hexagenia spp., and fathead minnow Pimephales promelas. Depuration (25 d) of PCBs was measured in organisms that had been transferred to clean sediment after the 28-d exposure. Uptake and elimination of PCBs was rapid in L. variegatus and Hexagenia spp. Tissue residues reached steady-state concentrations within 28 d; elimination rates and biota-sediment accumulation factors (BSAFs) of the PCB congeners were not correlated with K(OW). Uptake and elimination rates of PCBs were slower in P. promelas, and it is not clear whether steady-state was reached in fish tissues. Elimination rates of the PCB congeners significantly decreased with increasing K(OW) in fish. The appropriateness of a 28-d exposure for measuring steady-state concentrations in tissue of the invertebrates was confirmed, but further study is required for fish.     

Phosphorus speciation in manure and manure-amended soils using XANES spectroscopy

Previous studies suggested an increase in the proportion of calcium phosphates (CaP) of the total phosphorus (P) pool in soils with a long-term poultry manure application history versus those with no or limited application histories. To understand and predict long-term P accumulation and release dynamics in these highly amended soils, it is important to understand what specific P species are being formed. We assessed forms of CaP formed in poultry manure and originally acidic soil in response to different lengths of mostly poultry manure applications using P K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Phosphorus K-edge XANES spectra of poultry manure showed no evidences of crystalline P minerals but dominance of soluble CaP species and free and weakly bound phosphates (aqueous phosphate and phosphate adsorbed on soil minerals). Phosphate in an unamended neighboring forest soil (pH 4.3) was mainly associated with iron (Fe) compounds such as strengite and Fe-oxides. Soils with a short-term manure history contained both Fe-associated phosphates and soluble CaP species such as dibasic calcium phosphate (DCP) and amorphous calcium phosphate (ACP). Long-term manure application resulted in a dominance of CaP forms confirming our earlier results obtained with sequential extractions, and a transformation from soluble to more stable CaP species such as beta-tricalcium calcium phosphate (TCP). Even after long-term manure application (> 25 yr and total P in soil up to 13,307 mg kg(-1)), however, none of the manure-amended soils showed the presence of crystalline CaP. With a reduction or elimination of poultry manure application to naturally acidic soils, the pH of the soil is likely to decrease, thereby increasing the solubility of Ca-bonded inorganic P minerals. Maintaining a high pH is therefore an important strategy to minimize P leaching in these soils.     

The influence of steam injection for Enhanced Oil Recovery (EOR) on the quality of crude oil

Currently, due to reduction of oil reservoirs and the increasing need for oil as the main source for world energy, the need for production of heavy oil reservoirs is inevitable. The main purpose of this study is to determine the effectiveness of some operational and reservoir parameters and their impact on thermal and productive efficiency of thermal process of steam injection and quality of crude oil. In order to model the process, Eclipse-300 simulator was employed. Detection of these parameters, in addition to determining the best production scenario, can lead to the use of this method with better economic conditions. Hence, the results obtained from this study show that the optimal values obtained for operational parameters of stream injection such as steam quality, steam injection pressure, injection rate and well completion injection depth. The simulation results show that the use of optimal values of steam injection parameters can enhance efficiency of steam injection method and can make this method considered as third EOR method in heavy oil reservoirs than previously known in the petroleum industry.     

Terror management theory and self-esteem: Evidence that increased self-esteem reduced mortality salience effects.

On the basis of the terror management theory proposition that self-esteem provides protection against concerns about mortality, it was hypothesized that self-esteem would reduce the worldview defense produced by mortality salience (MS). The results of Exps 1 (49 undergraduates) and 2 (50 undergraduates) confirmed this hypothesis by showing that individuals with high self-esteem (manipulated in Exp 1; dispositional in Exp 2) did not respond to MS with increased worldview defense, whereas individuals with moderate self-esteem did. The results of Exp 3 (48 undergraduates) suggested that the effects of the 1st 2 experiments may have occurred because high self-esteem facilitates the suppression of death constructs following MS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex intracranial aneurysms: combined operative and endovascular approaches

OBJECTIVE: Endovascular management of complex intracranial aneurysms is increasingly being considered as an alternative to standard surgical clipping. However, little attention has been paid to the complementary nature of surgery and endovascular therapy. METHODS: Between September 1992 and May 1997, 12 patients with complex intracranial aneurysms were treated with combined operative and endovascular methods. Seven patients demonstrated subarachnoid hemorrhage (two of Grade II, two of Grade III, and three of Grade IV). Five patients demonstrated unruptured aneurysms, i.e., three giant aneurysms (one vertebrobasilar junction aneurysm, one middle cerebral artery bifurcation aneurysm, and one internal carotid artery-ophthalmic artery aneurysm), one large internal carotid artery-ophthalmic artery aneurysm, and one middle cerebral artery serpentine aneurysm. Management strategies involved either surgery followed by endovascular therapy (S-E; n = 5) or endovascular therapy followed by surgery (E-S; n = 7). S-E paradigms included aneurysm exploration followed by endovascular treatment (S-E1; n = 3), partial aneurysm clipping followed by endovascular aneurysm packing (S-E2; n = 1), and extracranial-to-intracranial bypass followed by endovascular parent vessel occlusion (S-E3; n = 1). E-S paradigms included superselective angiography followed by surgical clipping (E-S1; n = 2), Guglielmi detachable coil partial dome packing followed by delayed surgical clipping (E-S2; n = 2), proximal temporary vessel balloon occlusion followed by aneurysm clipping (E-S3; n = 2), and proximal permanent vessel occlusion followed by surgical aneurysm decompression for mass effect treatment (E-S4; n = 1). RESULTS: Eleven aneurysms (92%) were completely eliminated. The remaining aneurysm was 90% obliterated and remained quiescent at the 34-month follow-up examination, despite presenting with subarachnoid hemorrhage. No patient experienced repeat bleeding (follow-up period, 23+/-28 mo). There were no deaths. One patient achieved a fair outcome (Glasgow Outcome Scale score of III); all other patients experienced excellent outcomes (Glasgow Outcome Scale score of I). In all cases, the aneurysm management paradigm chosen had a positive effect on definitive therapy. CONCLUSION: Several factors can contribute to the complexity of intracranial aneurysms. Management strategies that combine operative and endovascular techniques in a complementary way, for the best possible outcomes for these patients, can be designed accordingly.     

Early prostate cancer detection and potential for surgical cure in men with poorly differentiated tumors

Postgastrectomy osteopenia is observed generally in humans. Fructooligosaccharides increase the absorption of calcium from the large intestine of healthy rats. Thus, we have examined whether they stimulate calcium absorption and prevent osteopenia in rats following total gastrectomy. Rats were subjected to either a sham surgical operation or Billoth II gastrectomy. Seven rats from each surgical treatment group were fed a control diet, and another seven rats of each treatment group were fed a diet containing fructooligosaccharides (75 g/kg diet) for 4 wk. For 5 d each week, feces were collected, and the calcium and phosphorus contents were measured for calculation of the absorption of these minerals. At the end of the experiment, the rats were killed and bones were collected. The net calcium absorption, calcium content and bone mineral density of the femur and tibia in gastrectomized rats fed the control diet were significantly less than those in sham-operated rats fed control diet. The net calcium absorption in rats fed the fructooligosaccharides diet was greater than that in rats fed control diet. Moreover, dietary fructooligosaccharides prevented the decrease in the calcium content and bone mineral density in gastrectomized rats. Dietary fructooligosaccharides enhanced calcium absorption and prevented the changes indicative of postgastrectomy osteopenia such as decreases in bone calcium content and bone mineral density in gastrectomized rats.     

Pioneers in Partnership: Lesbian and Gay Male Couples in Civil Unions Compared With Those Not in Civil Unions and Married Heterosexual Siblings.

This study compared 212 lesbians and 123 gay men who had civil unions in Vermont (during the first year legislation made this available) with 166 lesbians and 72 gay men in their friendship network who had not had civil unions, and also with 219 heterosexual married women and 193 heterosexual married men consisting of civil union couples' siblings and their spouses. Married heterosexual couples had been together longer and had more traditional division of labor and child care than did lesbians and gay men in both types of couples. Lesbians in civil unions were more open about their sexual orientation than those not in civil unions, and gay men in civil unions were closer to their family of origin than gay men not in civil unions. This is the first study on same-sex couples with civil unions, and the first to compare lesbians and gay men with their married siblings. At a time of legal changes for same-sex couples, these results indicate that legalized same-sex relationships are related to visibility of same-sex couples to their family and the general public. (PsycINFO Database Record (c) 2010 APA, all rights reserved)