Electrochemical determination of trihalomethanes in water by means of stripping analysis

A protocol has been developed and evaluated for the determination of trihalomethanes (THMs) at the submicromolar concentration level in water. This method is based on a three-step stripping analysis that utilizes a single electrochemical cell and that entails (a) direct electrochemical reduction of a trihalomethane at a silver cathode to form halide ions in an aqueous sample containing tetraethylammonium benzoate, (b) capture of the released halide ions as a silver halide film on the surface of a silver gauze anode, and (c) cathodic reduction and quantitation of the silver halide film by means of differential pulse voltammetry. Using this procedure, we have determined THMs individually; bromoform and chloroform have been successfully quantitated in 30 min and with a detection limit of 3.0 μg L(-1) (12 nM) and 6.0 μg L(-1) (50 nM), respectively. In addition, we have employed our methodology to determine the total trihalomethane (TTHM) content in a prepared water sample at a level commensurate with the maximum allowable annual average of 80 μg L(-1) mandated by the United States Environmental Protection Agency. We have compared our TTHM results to those obtained by an independent testing laboratory.     

Octopods versus concave nanocrystals: control of morphology by manipulating the kinetics of seeded growth via co-reduction

Au/Pd octopods and concave core@shell Au@Pd nanocrystals have been prepared by coupling for the first time a seed-mediated synthetic method with co-reduction. The integration of these two methods is central to the formation of these binary Au/Pd nanocrystals wherein the kinetics of seeded growth are manipulated via the co-reduction technique to control the final morphology of the nanocrystals. Significantly, the synthesis of these structures under similar reaction conditions illustrates that they are structurally related kinetic products. Detailed characterization by STEM-EDX analysis highlights the unique structural features of these nanocrystals and indicates that Pd localizes on the higher-energy features of the nanocrystals. Optical and electrocatalytic characterization also demonstrates their promise as a new class of multifunctional nanostructures.     

College adults are not good at self-regulation: A study on the relationship of self-regulation, note taking, and test taking.

Self-regulation supposedly plays a central role in memory and learning, especially for adults. Research using simple materials has found that adults are skilled self-regulators. Research using difficult materials has found the opposite. Using difficult materials, the authors attempted to improve college students' self-regulation by allowing extended study time before taking a test. The authors also examined whether background knowledge and note-taking strategies would be positively related to self-regulation. Results indicated that college students were not good at self-regulation, background knowledge and note taking were not related to self-regulation, and note taking and background knowledge were generally better predictors of test performance than self-regulation. Results imply that test performance is more related to note taking and background knowledge than to self-regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of encoding variability, processing activity, and rule–examples sequence on the transfer of conceptual rules.

Meaningful activity (relative to a more rote activity) and exposure to concepts in a variety of situations (as opposed to one situation) were hypothesized to positively influence the breadth of concept acquisition. 198 undergraduates performed concept-acquisition tasks, which involved learning the concept definitions and practice with examples, and completed a recognition test 2 days later. Examples of concepts on the criterion test represented a variety of contexts. Results indicate that more meaningful activity at the time of learning significantly facilitated overall performance on the criterion test. Though all Ss did comparably well on tests of concepts from a restricted context, those exposed to greater variations at the time of learning were significantly better at recognizing broader concept applications. Both concept definitions followed immediately by practice examples, and practice examples given the 1st day with concept definitions given just prior to the test produced better recall than practice examples followed immediately by concept definitions. Results are discussed in terms of the contextualist model for understanding the effects of these variables on learning, memory, and the outcomes of instruction. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of Milfoil (Myriophyllum Spicatum L.) on Phosphorus Movement Between Sediment and Water

Milfoil (Myriophyllum spicatum L.), grown in 10-liter battery jars and rooted in pond sediment, showed no leakage of P from the shoots into the surrounding water, even when P concentration in the water was 5 μg/L but 1000 μg/L in sediment water around the roots. P added to the water dropped to concentrations of about 10 μg/L in both planted and sediment only jars, but fell somewhat faster when milfoil was growing in the jars. This particular type of milfoil in its rapidly growing stage absorbed P through its leaves and stems and did not show any signs of acting as a conduit for increased movement of soluble P from enriched sediment water to overlying water, compared to sediment-water jars with no plants. When dissolved P levels were maintained at low levels (10 μg/L in the water), root absorption could not supply enough P to maintain plant tissues at their initial P content of about 0.80 percent, dry wt. No changes in sediment P over the course of the experiment could be assigned to the plants’ presence.