The knowledge illusion: who is doing what thinking?

Focusing on students’ attempts to explain the relative significance of different factors in Hitler’s rise to power, Catherine McCrory explores the vexed question of why students who seem able to express necessary historical knowledge on one occasion cannot effectively reproduce it on another. Drawing on a detailed analysis of what it actually means to ‘know’ something, she plans a series of accessible activities allowing as many students as possible to secure essential knowledge for themselves, rather than simply relying on the authority of the teacher who told them. She goes on to explain how careful diagnosis of the gaps between what students say and the reasoning that underpins their utterances can help teachers to decide where they can usefully ‘give’ students particular insights and where the students need to ‘arrive at’ those insights through their own cognitive labou

Dietary patterns among Vietnamese and Hispanic immigrant elementary school children participating in an after school program

Immigrants in the U.S. may encounter challenges of acculturation, including dietary habits, as they adapt to new surroundings. We examined Vietnamese and Hispanic immigrant children's American food consumption patterns in a convenience sample of 63 Vietnamese and Hispanic children in grades four to six who were attending an after school program. Children indicated the number of times they consumed each of 54 different American foods in the past week using a food frequency questionnaire. We ranked each food according to frequency of consumption, compared the intake of foods to the USDA Healthy Eating Pattern, and performed dietary pattern analysis. Since the data were not normally distributed we used two nonparametric tests to evaluate statistical significance: the Kruskal-Wallis tested for significant gender and ethnicity differences and the Wilcoxon signed-rank test evaluated the food consumption of children compared with the USDA recommended amounts. We found that among USDA categories, discretionary food was most commonly consumed, followed by fruit. The sample as a whole ate significantly less than the recommended amount of grains, protein foods, and dairy, but met the recommended amount of fruit. Boys ate significantly more grains, proteins, and fruits than did girls. Dietary pattern analysis showed a very high sweet snack consumption among all children, while boys ate more fast food and fruit than girls. Foods most commonly consumed were cereal, apples, oranges, and yogurt. Ethnicity differences in food selection were not significant. The high intake of discretionary/snack foods and fruit, with low intake of grains, vegetables, protein, and dairy in our sample suggests Vietnamese and Hispanic immigrant children may benefit from programs to improve diet quality

Is every toric variety an M-variety?

A complex algebraic variety X defined over the real numbers is called an M-variety if the sum of its Betti numbers (for homology with closed supports and coefficients in Z/2) coincides with the corresponding sum for the real part of X. It has been known for a long time that any nonsingular complete toric variety is an M-variety. In this paper we consider whether this remains true for toric varieties that are singular or not complete, and we give a positive answer when the dimension of X is less than or equal to 3.Comment: 13 page

Studies of Cobalt-Mediated Electrocatalytic CO_2 Reduction Using a Redox-Active Ligand

The cobalt complex [Co^(III)N_4H(Br)_2]+ (N_4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(7),2,11,13,15-pentaene) was used for electrocatalytic CO_2 reduction in wet MeCN with a glassy carbon working electrode. When water was employed as the proton source (10 M in MeCN), CO was produced (f_(CO)= 45% ± 6.4) near the Co^(I/0) redox couple for [Co^(III)N_4H(Br)_2]+ (E_(1/2) = −1.88 V FeCp_2^(+/0)) with simultaneous H_2 evolution (f_(H2)= 30% ± 7.8). Moreover, we successfully demonstrated that the catalytically active species is homogeneous through the use of control experiments and XPS studies of the working glassy-carbon electrodes. As determined by cyclic voltammetry, CO_2 catalysis occurred near the formal CoI/0redox couple, and attempts were made to isolate the triply reduced compound (“[Co^0N_4H]”). Instead, the doubly reduced (“Co^I”) compounds [CoN4] and [CoN_4H(MeCN)]+ were isolated and characterized by X-ray crystallography. Their molecular structures prompted DFT studies to illuminate details regarding their electronic structure. The results indicate that reducing equivalents are stored on the ligand, implicating redox noninnocence in the ligands for H_2 evolution and CO_2 reduction electrocatalysis

A 10^6‑Fold Enhancement in N_2‑Binding Affinity of an Fe_2(μ-H)_2 Core upon Reduction to a Mixed-Valence Fe^(II)Fe^I State

Transient hydride ligands bridging two or more iron centers purportedly accumulate on the iron–molybdenum cofactor (FeMoco) of nitrogenase, and their role in the reduction of N_2 to NH_3 is unknown. One role of these ligands may be to facilitate N_2 coordination at an iron site of FeMoco. Herein, we consider this hypothesis and describe the preparation of a series of diiron complexes supported by two bridging hydride ligands. These compounds bind either one or two molecules of N_2 depending on the redox state of the Fe_2(μ-H)_2 unit. An unusual example of a mixed-valent Fe^(II)(μ-H)^2Fe^I is described that displays a 10^6-fold enhancement of N_2 binding affinity over its oxidized congener, quantified by spectroscopic and electrochemical techniques. Furthermore, these compounds show promise as functional models of nitrogenase as substantial amounts of NH_3 are produced upon exposure to proton and electron equivalents. The Fe(μ-H)Fe(N2_) sub-structure featured herein was previously unknown. This subunit may be relevant to consider in nitrogenases during turnover

Evaluating Activity for Hydrogen-Evolving Cobalt and Nickel Complexes at Elevated Pressures of Hydrogen and Carbon Monoxide

Molecular cobalt and nickel complexes are among the most promising homogeneous systems for electrocatalytic hydrogen evolution. However, there has been little exploration into the effect of gaseous co-additives such as CO and H_2, which may be present in operating hydrogen-evolving or carbon-dioxide reduction systems, on the performance of these molecular electrocatalysts. In this report, we investigate the electrocatalytic activity of six cobalt and nickel complexes supported by tetraazamacrocyclic or diazadiphosphacyclooctane ligands for the reduction of p-toluenesulfonic acid to hydrogen in acetonitrile under inert atmosphere and in the presence of CO and H_2. We present an elevated-pressure electrochemical apparatus capable of reaching CO and H_2 pressures of ca. 15–520 pounds per square inch (psia) (∼1–35 atm), and we use this apparatus to determine binding constants for CO addition for each catalyst and study the inhibition of the electrocatalysis as a function of CO and H_2 pressure. In the case of CO, the extent of catalytic inhibition is correlated to the binding constant, with the cobalt complexes showing a greater degree of catalyst inhibition compared to the nickel complexes. In the case of H2, no complex showed appreciable electrocatalytic inhibition even at H_2 pressures of ca. 500 psia

Examining plausibility of self-report energy intake data: considerations for method selection.

Self-reported dietary intake data contain valuable information and have long been used in the development of nutrition programs and policy. Some degree of measurement error is always present in such data. Biological plausibility, assessed by determining whether self-reported energy intake (rEI) reflects physiological status and physical activity level, must be examined and accounted for before drawing conclusions about intake. Methods that may be used to account for plausibility of rEI include crude methods such as excluding participants reporting EIs at the extremes of a range of intake and individualized methods such as statistical adjustment and applying cutoffs that account for the errors associated with within-participant variation in EI and total energy expenditure (TEE). These approaches allow researchers to determine how accounting for under- and overreporting affects study results and to appropriately address misreporting in drawing conclusions with data collected and in interpreting reported research. In selecting a procedure to assess and account for plausibility of intake, there are a number of key considerations, such as resources available, the dietary-report instrument, as well as the advantages and disadvantages of each method. While additional studies are warranted to recommend one procedure as superior to another, researchers should apply one of the available methods to address the issue of implausible rEI. If no method is applied, then at minimum, mean TEE or rEI/TEE should be reported to allow readers to ascertain the degree of misreporting at a gross level and better interpret the data and results provided