Pedagogical content knowledge and content knowledge of secondary mathematics teachers.

Drawing on the work of L. S. Shulman (1986), the authors present a conceptualization of the pedagogical content knowledge and content knowledge of secondary-level mathematics teachers. They describe the theory-based construction of tests to assess these knowledge categories and the implementation of these tests in a sample of German mathematics teachers (N=198). Analyses investigate whether pedagogical content knowledge and content knowledge can be distinguished empirically, and whether the mean level of knowledge and the degree of connectedness between the two knowledge categories depends on mathematical expertise. Findings show that mathematics teachers with an in-depth mathematical training (i.e., teachers qualified to teach at the academic-track Gymnasium) outscore teachers from other school types on both knowledge categories and exhibit a higher degree of cognitive connectedness between the two knowledge categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Sensitive and Robust Method for Direct Determination of Lipolytic Activity in Natural Milk Environment

Microbial lipases may be produced during milk storage and processing. This can lead to organoleptic changes in the corresponding dairy products. Thus, monitoring of lipase activity in milk is desirable. Turbidity of milk prevents a direct photometric measurement of lipase activity using chromophore- or fluorophore-based assays. Laborious pretreatments or alternative analytical methods normally have to be used. With the method for the determination of lipolytic activity (MeDeLi) proposed here, it is possible to measure lipase activity directly in the natural milk utilizing tailored fluorometric substrates. Only a defatting step is carried out initially for the MeDeLi. Then, the conversion of added lipase substrate is carried out in the unmodified milk without addition of any solutions or any enzyme extraction procedure which may influence the enzyme activity. Thereafter, the milk sample is treated with two solutions to remove the turbidity of milk by dissolution. A valid and sensitive fluorometric measurement is then possible. The applicability of the MeDeLi was demonstrated in comparison with tests published previously: The limit of detection for lipolytic activity measured by MeDeLi was the lowest, with 41 pkat/mL. Raw milk, milk products, and spoiled milk samples were also investigated with the MeDeLi.     

Electronic Markets for Architects—The Architecture of Electronic Markets

In recent years there has been a move towards more cooperation in the construction industry. While the traditional practice is that the architect chooses the trades, provides the construction plan, and tells the trades what to do, a new initiative has been formed to create cooperative construction teams. Here the architect will discuss details of the construction plan with the trades concerned and all parties work cooperatively on the construction project. This means that there will be many coordination tasks and that communication plays a pivotal role. The paper presents a framework for and an implementation of an electronic marketplace to support such cooperative construction teams. It will be argued that there must be a co-design of the business system (i.e. cooperative construction teams) and the IT system (i.e. the marketplace including the search, negotiation, and fulfilment phases) for efficiently supporting small and medium-sized companies participating in cooperative teams and interacting on electronic marketplaces.     

Effects of partial volume and phase shift between fat and water in gradient-echo magnetic resonance-mammography

The signal modulations caused by partial volume effect and phase shift between fat and water signal in gradient-echo magnetic resonance mammography (GRE MR-mammography) have been calculated. Based on this, the theoretical sensitivity and specificity of GRE MR-mammography has been investigated considering different evaluation methods for the gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA)-based signal enhancement. The results show that both in- and out-of-phase sequences suffer from partial volume effects in voxels that contain both fat and water. This can decrease sensitivity to Gd-DTPA uptake in small, fat-embedded lesions or in pathology that contains fat interspersed histologically. Additionally, out-of-phase sequences can suffer from phase cancellation effects that can further decrease their sensitivity to Gd-DTPA uptake. In the worst case signal can actually decrease during Gd-DTPA influx. Determination of enhancement relative to the baseline value can decrease the specificity of GRE MR-mammography in the out-of-phase condition and decrease the sensitivity in the in-phase condition. These effects are less pronounced when enhancement is calculated relative to fat. These effects need to be understood since Gd-DTPA uptake is the prime indicator of malignancy in MR-mammography.     

Quantitative structure–retention relationship modelling of esters on stationary phases of different polarity

The semi-empirical electrotopological index, I_SET, used for QSRR models, was developed and optimized to describe the chromatographic retention of saturated esters on the five different stationary phases (SE-30, OV-7, DC-710, OV-225 and XE-60). The simple linear regressions between the retention indices and the proposed index were of good statistical quality, high internal stability and good predictive ability for external groups, especially for the stationary phase with low polarity, showing that the specific molecular interactions occur on highly polar phases. For the esters, the interactions between the molecules and the stationary phase are slowly increased relative to hydrocarbons due to the charge redistribution that occurs in the presence of the heteroatom. These facts were included in the calculation of I_SET through a small increase in the SET_i values for heteroatoms and the carbon atoms attached to them. The increase in the SET_i values originates from the dipole moment of the whole molecule and an equivalent local dipole moment related to the net charges of the atoms belonging to the functional group and the carbon atoms attached to them. The polarity of the stationary phases, indicated by the retention polarity (P_R) given by Tarján, is reflected in the intercept of the equations obtained for each stationary phase. Thus, a single combined QSRR model was generated with a satisfactory predictive quality, including a parameter that represents the polarity retention of all stationary phases studied.     

Homework works if homework quality is high: Using multilevel modeling to predict the development of achievement in mathematics.

The present study examined the associations of 2 indicators of homework quality (homework selection and homework challenge) with homework motivation, homework behavior, and mathematics achievement. Multilevel modeling was used to analyze longitudinal data from a representative national sample of 3,483 students in Grades 9 and 10; homework effects were analyzed at the student and the class level simultaneously. Students who perceived their homework assignments to be well selected reported higher homework motivation, and homework behavior at both the student and the class level predicted later achievement at the class level. Homework assignments perceived to be cognitively challenging were differentially associated with achievement at the student and the class level. Students who perceived their homework to be challenging (student level) showed relatively poor performance, but homework challenge was positively related to achievement at the class level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cover Image,Volume 99, Issue 14

The cover image is based on the Short Communication Hydrolysis of chlorogenic acid in apple juice using a p-coumaryl esterase of Rhizoctonia solani by Mareike Siebert et al., https://doi.org/10.1002/jsfa.9940 .

     

The Collider Principle in Causal Reasoning: Why the Monty Hall Dilemma Is So Hard.

The authors tested the thesis that people find the Monty Hall dilemma (MHD) hard because they fail to understand the implications of its causal structure, a collider structure in which 2 independent causal factors influence a single outcome. In 4 experiments, participants performed better in versions of the MHD involving competition, which emphasizes causality. This manipulation resulted in more correct responses to questions about the process in the MHD and a counterfactual that changed its causal structure. Correct responses to these questions were associated with solving the MHD regardless of condition. In addition, training on the collider principle transferred to a standard version of the MHD. The MHD taps a deeper question: When is knowing about one thing informative about another? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhancing DPCD in Liquid Products by Mechanical Inactivation Effects: Assessment of Feasibility

The enhancement of standard dense phase carbon dioxide (DPCD) pasteurization by additional mechanical effects was assessed in this work. These effects were induced during pasteurization by the sudden depressurization in a narrow minitube. The high flow velocities, moderate pressures (40–80 bar) and low temperatures (25–45 °C) lead to intense degasification and shear stress. The inactivation of the test microorganism Escherichia coli DH5α (E. coli DH5α) was determined before and after depressurization in the minitube, representing entirely chemical DPCD via dissolved CO₂ and total inactivation comprising the effects of dissolved CO₂ and mechanical effects, respectively. Compared to conventional DPCD pasteurization, which is mostly attributed to chemical effects, the additional mechanical effects increased the inactivation efficiency considerably.