Effects of fluctuating river flow on groundwater/surface water mixing in the hyporheic zone of a regulated,large cobble bed river

Physicochemical relationships in the boundary zone between groundwater and surface water (i.e. the hyporheic zone) are controlled by surface water hydrology and the hydrogeologic properties of the riverbed. We studied how sediment permeability and river discharge altered the vertical hydraulic gradient (VHG) and water quality of the hyporheic zone within the Hanford Reach of the Columbia River. The Columbia River at Hanford is a large, cobble‐bed river where water level fluctuates up to 2 m daily because of hydropower generation. Concomitant with river stage recordings, continuous readings were made of water temperature, specific conductance, dissolved oxygen and water level of the hyporheic zone. The water level data were used to calculate VHG between the river and hyporheic zone. Sediment permeability was estimated using slug tests conducted in piezometers installed into the river bed. The response of water quality measurements and VHG to surface water fluctuations varied widely among study sites, ranging from no apparent response to covariance with river discharge. At some sites, a hysteretic relationship between river discharge and VHG was indicated by a time lag in the response of VHG to changes in river stage. The magnitude, rate of change and hysteresis of the VHG response varied the most at the least permeable location (hydraulic conductivity (K) = 2.9 × 10^?4 cms^?1) and the least at the most permeable location (K = 8.0 × 10^?3 cms^?1). Our study provides empirical evidence that sediment properties and river discharge both control the water quality of the hyporheic zone. Regulated rivers, like the Columbia River at Hanford, that undergo large, frequent discharge fluctuations represent an ideal environment in which to study hydrogeologic processes over relatively short time periods (i.e. days to weeks) that would require much longer periods (i.e. months to years) to evaluate in unregulated systems. Copyright © 2006 John Wiley & Sons Ltd.     

Addressees of performance goals.

As performance goals aim to both procure acknowledgment of one's abilities and to avoid revealing a lack of one's abilities, the authors hypothesized that students hold specific performance goals for different addressees and that there are specific correlational patterns with other motivational constructs. They analyzed a data set of 2,675 pupils (1,248 boys and 1,426 girls) attending Grades 8 and 9 (mean age=15.0, SD=0.97). The students completed a questionnaire consisting of 12 items measuring performance approach goals and 12 items measuring performance avoidance goals. In each subset, 4 groups of addressees were differentiated: parents, teachers, peers, and the acting individual him/herself. Additionally, several external criteria were measured. The authors concurrently tested theory-driven, structural equation models. Incorporating all 24 items, the best-fitting model was a multitrait-multimethod model, which posited 2 factors for approach and avoidance goals and 4 addressee factors. While performance goals addressing parents showed relationships to maladaptive motivational and learning patterns, performance goals addressing classmates and self showed relationships to adaptive motivational and learning patterns. The relationships between performance goals addressing teachers and external criteria were rather weak and unsystematic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Third cranial nerve palsy caused by gummatous neurosyphilis: MR findings

The clinical and MR findings in an unusual case of gummatous neurosyphilis are reported. A 44-year-old woman suffering from diplopia and right-sided headaches was admitted. Physical examination and routine laboratory parameters were normal except for a third-nerve palsy. MR images revealed a contrast-enhancing lesion of the upper brain stem and third cranial nerve. Differential diagnosis included neuroma of the third cranial nerve, as well as neurosarcoidosis and other inflammatory processes. Serologic tests and lumbar puncture revealed the presence of active syphilis. After intravenous treatment with penicillin G, follow-up MR examinations showed diminishing size of the lesion with its complete resolution within 3 months.     

Regulating self-organized collaborative learning: the importance of homogeneous problem perception,immediacy and intensity of strategy use

Very often, university students deliberately form self-organized study groups, e.g. to study collaboratively for an upcoming exam. Yet, very little is known about what regulation problems such self-organized study groups encounter during their learning process and how they try to cope with these problems. Therefore, this study investigates how completely self-organized groups (i.e., non-guided groups outside the classroom that form without external impulse) regulate their collaborative learning process when faced with different kinds of regulation problems. More specifically, we tested the hypotheses that members of self-organized study groups are more satisfied with their group learning experience (a) the more homogeneous their problem perceptions are within their group, (b) the more they apply immediate (rather than non-immediate) strategies to remedy their regulation problems, and (c) the more frequently they apply regulation strategies. In a longitudinal study, N?=?122 students, voluntarily studying for their exams in N?=?52 groups, were asked to indicate the types of problems they experienced, the types of strategies they used to tackle those problems, and their satisfaction with their group learning experience after each of their self-organized study meetings. Hierarchical linear modeling confirmed all hypotheses. Qualitative analysis of two selected groups’ self-reported situational data provided additional insights about the mechanisms that may have contributed to the results. Our study provides important directions for future research, including the recommendation to identify the processes by which groups (a) can reach homogeneity of problem perceptions and (b) coordinate the choice of appropriate strategies within the group.

     

Tracking sources of unsaturated zone and groundwater nitrate contamination using nitrogen and oxygen stable isotopes at the Hanford site, Washington

The nitrogen and oxygen isotopic compositions of nitrate in pore water extracts from unsaturated zone (UZ) core samples and groundwater samples indicate at least four potential sources of nitrate in groundwaters at the U.S. DOE Hanford Site in south-central Washington. Natural sources of nitrate identified include microbially produced nitrate from the soil column (delta15N of 4 - 8 per thousand, delta18O of -9 to 2 per thousand) and nitrate in buried caliche layers (delta15N of 0-8 per thousand, delta 18O of -6to 42 per thousand). Isotopically distinctindustrial sources of nitrate include nitric acid in low-level disposal waters (delta15N approximately per thousand, delta 18O approximately 23%o) per thousandnd co-contaminant nitrate in high-level radioactive waste from plutonium processing (6'5delta1of 8-33 % o, per thousand18delta oO -9 to 7%0). per thousandThe isotopic compositions of nitrate from 97 groundwater wells with concentrations up to 1290 mg/L NO3- have been analyzed. Stable isotope analyses from this study site, which has natural and industrial nitrate sources, provide a tool to distinguish nitrate sources in an unconfined aquiferwhere concentrations alone do not. These data indicate that the most common sources of high nitrate concentrations in groundwater at Hanford are nitric acid and natural nitrate flushed out of the UZ during disposal of low-level wastewater. Nitrate associated with high-level radioactive UZ contamination does not appear to be a major source of groundwater nitrate at this time.     

Iodine-123-iodobenzamide SPECT assessment of dopamine D2 receptor occupancy in riperidone-treated schizophrenic patients

The recently introduced neuroleptic, risperidone, was expected to block fewer dopamine D2 receptors than typical neuroleptics (e.g., haloperidol), but at comparable potency. The aim of this study was to evaluate the degree of dopamine D2 receptor occupancy in relation to the neuroleptic dosage and to correlate the findings with the presence of extrapyramidal symptoms (EPS). Additionally, the data were compared to previous iodobenzamide (IBZM) SPECT findings in patients treated with other neuroleptics, haloperidol and clozapine. METHODS: In 20 patients with schizophrenia [Diagnostic and Statistical Manual of Mental Disorders (Third Edition-Revised)] treated with mean daily doses of risperidone ranging from 0.029 to 0.128 mg/kg body weight, SPECT was performed 2 hr after intravenous injection of 185 MBq 123I-IBZM, a selective dopamine D2 receptor ligand. Striatal IBZM binding was assessed by calculating a striatal/frontal cortex ratio, expressed as a percentage of the control value. RESULTS: Selective dopamine D2 receptor binding of the ligand was reduced in all treated patients, with binding values ranging from 7% to 68%. The degree of occupancy displayed an exponential dose-response relationship (r = -0.86; p < 0.0001). The slope of the curve was between those of haloperidol and clozapine but was closer and more similar in shape to the curve of haloperidol. Extrapyramidal symptoms were observed in 8 of 20 patients with binding values between 7% and 47%. However, there was no clear relationship between the degree of receptor occupancy and the presence of EPS. CONCLUSION: The findings suggest an exponential dose-response relationship between the daily dosage of risperidone and the dopamine D2 receptor occupancy. The blockade of specific striatal IBZM binding found under therapy with risperidone is between those of haloperidol and clozapine. The dose-response curve for risperidone, however, shows greater similarity to that of haloperidol.     

Some considerations of reduction of reference phase error in phase-stepping interferometry

Positioning errors and miscalibrations of the phase-stepping device in a phase-stepping interferometer lead to systematic errors proportional to twice the measured phase distribution. We discuss the historical development of various error-compensating phase-shift algorithms from a unified mathematical point of view. Furthermore, we demonstrate experimentally that systematic errors can also be removed a posteriori. A Twyman-Green-type microlens test interferometer was used for the experiments.     

Design of computer-generated beam-shaping holograms by iterative finite-element mesh adaption

Computer-generated phase-only holograms can be used for laser beam shaping, i.e., for focusing a given aperture with intensity and phase distributions into a pregiven intensity pattern in their focal planes. A numerical approach based on iterative finite-element mesh adaption permits the design of appropriate phase functions for the task of focusing into two-dimensional reconstruction patterns. Both the hologram aperture and the reconstruction pattern are covered by mesh mappings. An iterative procedure delivers meshes with intensities equally distributed over the constituting elements. This design algorithm adds new elementary focuser functions to what we call object-oriented hologram design. Some design examples are discussed.     

Review: Technical and policy challenges in deep vadose zone remediation of metals and radionuclides

Contamination in deep vadose zone environments is isolated from exposure so direct contact is not a factor in its risk to human health and the environment. Instead, movement of contamination to the groundwater creates the potential for exposure and risk to receptors. Limiting flux from contaminated vadose zone is key for protection of groundwater resources, thus the deep vadose zone is not necessarily considered a resource requiring restoration. Contaminant discharge to the groundwater must be maintained low enough by natural attenuation (e.g., adsorption processes or radioactive decay) or through remedial actions (e.g., contaminant mass reduction or mobility reduction) to meet the groundwater concentration goals. This paper reviews the major processes for deep vadose zone metal and radionuclide remediation that form the practical constraints on remedial actions. Remediation of metal and radionuclide contamination in the deep vadose zone is complicated by heterogeneous contaminant distribution and the saturation-dependent preferential flow in heterogeneous sediments. Thus, efforts to remove contaminants have generally been unsuccessful although partial removal may reduce downward flux. Contaminant mobility may be reduced through abiotic and biotic reactions or through physical encapsulation. Hydraulic controls may limit aqueous transport. Delivering amendments to the contaminated zone and verifying performance are challenges for remediation.