Microbial dynamics in oil-impacted prairie soil

A remote site in the Tallgrass Prairie Preserve (Osage County, OK) was contaminated with crude oil by a pipeline break in 1992. In 1996, the contaminated soil was bioremediated by blending with uncontaminated soil, prairie hay, buffalo manure, and commercial fertilizers, and spreading in a shallow layer over uncontaminated soil to create a landfarm. The landfarm was monitored for two years for aerobic and anaerobic bacteria, soil gases indicative of microbial activity, and for changes in the concentration of total petroleum hydrocarbons (TPH). Levels of hydrocarbon degraders and soil gas indicators of aerobic degradation were stimulated in the landfarm during the first warm season relative to uncontaminated prairie soil. However, these same indicators were less conclusive during the second warm season, indicating depletion of the more easily degradable hydrocarbons, although the landfarm still contained 6,800 mg/kg TPH on the average at the beginning of the second warm season. Methane formation and methanogen counts were clearly stimulated in the first warm season relative to uncontaminated prairie soil, in dicating that methanogenesis plays an important role in the mineralization of hydrocarbons even in these shallow soils.     

Reporting a network’s most-central actor with a confidence level

This article introduces a confidence level (CL) statistic to accompany the identification of the most central actor in relational, social network data. CL is the likelihood that the most-central actor assertion is correct in light of imperfect network data. The CL value is derived from a frequency-based probability according to perturbed samples of feature-equivalent network data. Analysts often focus attention towards the most central, highest valued, top actor [or node] according to one of four traditional measures: degree, betweenness, closeness or eigenvector centrality. However, given that collected social network data often has missing relational links, the correctness of the top-actor claim becomes uncertain. This paper describes and illustrates a practical approach for estimating and applying a CL to the top-actor identification task. We provide a simple example of the technique used to derive a posterior probability, then apply the same approach to larger, more pragmatic random network by using the results of an extensive virtual experiment involving uniform random and scale-free topologies. This article has implications in organizational practice and theory; it is simple and lays groundwork for developing more intricate estimates of reliability for other network measures.     

EQUIP: a worldwide program to ensure the quality of urinary iodine procedures

In 2001 the Centers for Disease Control and Prevention (CDC) established a program, Ensuring the Quality of Urinary Iodine Procedures (EQUIP); to assist laboratories around the world and assess the accuracy of their urinary iodine (UI). CDC designed EQUIP to issue unknown specimens to participating laboratories three times per year. Each laboratory was asked to analyze unknown samples in duplicate on three different days. During the first five rounds of EQUIP, 41 laboratories participated, measuring unknown samples and reporting their results to CDC. CDC used these results to prepare a statistical report for the laboratories. Feedback to the laboratories provided external confirmation regarding performance. As a group, laboratory performance improved; several laboratories made considerable improvement. Several laboratories that showed no improvement have ordered new equipment or are arranging for additional training. EQUIP is a key tool used to support laboratory quality assurance in an effort to eliminate iodine deficiency disorders (IDD) in the world.

Buffers for the physiological pH range: Thermodynamic constants of substituted aminopropanesulfonic acids from 5 to 55°C

ThepK ₂ values for 3-[(l,l-Dimethyl-2-hydroxymethyl)amino]-2-hydroxypropanesulfonic acid (AMPSO), and 3-[N,N-Bis(-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have been determined at 12 temperatures over the range 5 to 55‡C by measurements of the emf of cells without liquid junction containing hydrogen and silver-silver chloride electrodes. The values of pK ₂ for AMPSO and DIPSO were found to be 9.138 and 7.576, respectively, at 25‡C. The thermodynamic quantities, δG‡, δH‡, δS‡, and δC _p ^‡ were calculated from the change of the equilibrium constants with temperature. These buffer substances are useful as secondary pH standards in the physiological region of pH 7 to 9. Camille and Henry Dreyfus Fellow, 1994–1996.     

Controlled polymerization of α-methyl-β-pentyl-β-propiolactone by a discrete zinc alkoxide complex

We report the zinc(II) alkoxide-mediated ring opening polymerization of α-methyl-β-pentyl-β-propiolactone. The polymerization proceeds to high conversion and in the absence of significant transesterification to yield polymers with narrow molecular weight distributions. Poly(α-methyl-β-pentyl-β-propiolactone), PMPP, is an amorphous, low glass transition material that forms immiscible blends with polylactide (PLA). PMPP-b-PLA diblock copolymers, for use as potential blend compatibilizers, were synthesized in a controlled manner by sequential monomer addition.     

Reactions of (η-allyl)dicarbonylmolybdenum(II) complexes with phosphorus and arsenic donor ligands

Reaction of [MoX(CO)₂(η-C₃H₅)(MeCN)₂] with the arsines Ph₂AsCH₂CH₂AsPh₂ (dae) and Ph₂AsCH₂AsPh₂ (dam) yields complexes of stoichiometry [MoX(CO)₂(η-C₃H₅)dae] (where X = Cl, Br or I) and [MoX(CO)₂(η-C₃H₅)]₂dam (where X = Cl or Br). The former are isomorphous with the known Ph₂PCH₂CH₂PPH₂ complexes, whereas the latter probably contain halogen and dam bridges. Under forcing conditions the corresponding ditertiary phosphines form the molybdenum(0) derivatives $\text{cis}$-Mo(CO)₂(Ph₂P(CH₂)_nPPh₂]₂ (where n = 1 or 2).     

Cell-active dual specificity phosphatase inhibitors identified by high-content screening

Phosphorylation of extracellular signal-regulated kinase (Erk) is tightly controlled by dual specificity phosphatases (DSPases), but few inhibitors of Erk dephosphorylation have been identified. Using a high-content, fluorescence-based cellular assay and the National Cancer Institute's 1990 agent Diversity Set, we identified ten compounds (0.5%) that significantly increased phospho-Erk cytonuclear differences in intact cells. Three of the ten positive compounds inhibited the mitogen-activated protein kinase phosphatase-3 (MKP-3/PYST-1) in vitro without affecting VHR or PTP1B phosphatases. The most potent inhibitor of MKP-3 had an IC(50) of <10 microM and inhibited MKP-3 in a novel, fluorescence-based multiparameter chemical complementation assay. These results suggest that the phospho-Erk nuclear accumulation assay may be a useful tool to discover DSPase inhibitors with biological activity.     

Teacher Learning and Mathematics Manipulatives: A Collective Case Study About Teacher Use of Manipulatives in Elementary and Middle School Mathematics Lessons

This collective case study analyzes the use of manipulatives in math lessons developed and taught by 4 groups of elementary teachers (K‐8) involved in lesson study as part of a professional development program. The study found that in three of four lessons studied manipulative use was turned into an end in and of itself, rather than a tool, and that in the fourth lesson manipulative use hindered rather than helped student learning. These problems with manipulative use by teachers in the lessons provide helpful guidance for planning of future professional development for math teaching. Our conclusion contains recommendations for successful implementation of manipulatives for both teachers and professional developers. Most importantly, we stress the need to emphasize the link between pedagogy and content, not the specific use of manipulatives.     

An ab initio study of S(N)2 reactivity at C6 in hexopyranose derivatives. I. Influence of dipole-dipole interactions in the transition structure

It is widely accepted that dipole-dipole interactions in the S(N)2 transition structure can play a dominant role in determining reaction rates. A model of this type was proposed some years ago to explain the remarkably low reactivity of galactopyranose-6-O-sulfonates toward S(N)2 displacement, and similar arguments have recently been restated in the context of gas-phase reactions. In this paper, we present ab initio calculations (B3LYP/6-31+G(d,p)) on model structures and an analysis of charge densities using the theory of atoms in molecules. We find that the maximum possible impact of local dipole-dipole interactions is insufficient to account for the observed reactivity differences.