Relationship Between Professional Development,Teachers' Instructional Practices,and the Achievement of Students in Science and Mathematics

The purpose of this study was to examine the relationship between different types of professional development, teachers' instructional practices, and the achievement of students in science and mathematics. The types of professional development studied included immersion, examining practice, curriculum implementation, curriculum development, and collaborative work. Data regarding teachers' instructional practices and the amount of professional development were collected using teacher surveys. Ninety‐four middle school science teachers and 104 middle school mathematics teachers participated in the study. Student achievement was measured using eighth grade state science and mathematics achievement test data. Regression analyses suggested that for both science and mathematics teachers, examining practice and curriculum development were significantly related to the use of standards‐based instructional practices. Only curriculum development for mathematics teachers was significantly related to student achievement. Implications of results for the professional development of science and mathematics teachers are discussed.     

Positivity for Gaussian graphical models

Gaussian graphical models are parametric statistical models for jointly normal random variables whose dependence structure is determined by a graph. In previous work, we introduced trek separation, which gives a necessary and sufficient condition in terms of the graph for when a subdeterminant is zero for all covariance matrices that belong to the Gaussian graphical model. Here we extend this result to give explicit cancellation-free formulas for the expansions of non-zero subdeterminants.     

Comparison of total folate concentrations in foods determined by microbiological assay at several experienced U.S. commercial laboratories

Analysis of total folate concentration measured by microbiological assay in a variety of foods submitted in a routine manner to experienced laboratories that regularly perform folate analysis on fee-for-service basis was evaluated. Homogenates of fresh strawberries, frozen spinach, orange juice, frozen meat and vegetable pizza, dry macaroni, and dried pinto beans were prepared and stored under conditions previously determined to maintain stability of folate content. An aliquot of each composite and of 3 certified reference materials were sent on each of 4 occasions to 4 laboratories. Results for macaroni and pizza, the only folic acid-fortified foods, had considerably lower between-laboratory variation (CV(B)) with CV(B) of 9-11% versus >45% for other foods. Mean total folate ranged from 14 to 279 microg/100 g for a mixed vegetable reference material, from 5 to 70 microg/100 g for strawberries, and from 28 to 81 microg/100 g for wholemeal flour. Only 1 laboratory reported using a tri-enzyme extraction, and all laboratories used folic acid fortified foods as internal control materials. Users of commercial total folate analysis should understand the uncertainty in values determined by microbiological assay, particularly for foods containing primarily naturally occurring folate, which may not be apparent when replicate samples are not submitted for analysis.     

Derivatives of pentamidine designed to target the Leishmania lipophosphoglycan

The Leishmania lipophosphoglycan (LPG) is the most abundant cell surface glycoconjugate of a family of infectious protozoa. Pentamidine, a common drug used in the treatment of Leishmania infections, has been modified with boronic acids so that it might bind more selectively to the phosphodisaccharide repeating unit of the LPG. This could serve to target the drug to the protozoan surface and increase its efficacy in vivo.     

Rules of Macrocycle Topology: A [13]‐Macrodilactone Case Study

Shape is an inherent trait of a molecule that dictates how it interacts with other molecules, either in binding events or intermolecular reactions. Large‐ring macrocyclic compounds in particular leverage their shape when they are selectively bound by biomolecules and also when they exhibit macrocyclic diastereoselectivity. Nonetheless, rules that link structural parameters to the conformation of a macrocycle are still rudimentary. Here we use a structural investigation of a family of [13]‐macrodilactones as a case study to develop rules that can be applied generally to macrocycles of different sizes and with a variety of functionality. A characteristic “ribbon” shape is adopted by the [13]‐macrodilactones in the absence of stereogenic centres, which exhibits planar chirality. When one stereogenic centre at key positions on the backbone is incorporated into the structure, the planar chirality is dictated by the configuration of the centre. In cases where two stereogenic centres are present, their relationships can either reinforce the characteristic ribbon shape or induce alternative shapes to be adopted. The rules established in the case study are then applied to the analysis of a structure of the natural product migrastatin. They lay the groundwork for the development of models to understand macrocycle‐biomolecule interactions and for the preparation of macrocycles with designed properties and activities.     

Investigation of fiber motion near solid boundaries in simple shear flow

In this paper, fiber motion near a planar wall was investigated using a planar shear flow apparatus. Fibers were placed (one at a time) perpendicular to the flow direction at various locations throughout the flow field. The location and orientation of each fiber versus time was measured, using an image processing system, until the fiber aligned with the flow direction. When the centroid of the fiber was located at distances greater than a fiber length from the wall, Jeffery's equations governing particle motion were verified. For distances less than a fiber length and greater than a fiber diameter from the wall, the fiber experienced an increased rate of rotation. In this regime, the motion of the fiber could be described by Jeffery's equations if an increased effective shear rate was used. The effective shear rate was found to increase logarithmically with decreasing separation distance. The wall effect was higher for longer aspect ratio fibers and was also a function of orientation; fibers oriented perpendicular to the wall rotated faster than those oriented parallel to the wall at the same separation distance. Once the fiber aligned with the flow direction, it ceased to rotate within the field of view. In this orientation, the wall had a stabilizing effect on the fiber. In efforts to relate the increase in shear rate to the aspect ratio of the fiber and the separation distance between the fiber and a solid wall, a translation model based on the work of De Mestre and Russel was explored. This model allows one to quantify the increase in shear rate experienced by the fiber due to the presence of a wall or obstruction in the flow field. However, the model has its limitations and care should be taken when applying this model outside its realm of validity. When compared to experimental data, the translation model provides a very good estimate of the increased shear rate experienced by the fiber when it is located less than 2/3 of a fiber length from a planar wall. Received: 20 April 2000 Accepted: 28 September 2000     

An efficient (1)H/(31)P double-resonance solid-state NMR probe that utilizes a scroll coil

The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of (1)H and (31)P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples.     

Science and Mathematics Instruction in a Reform‐based Teacher Preparation Program

This study examined the science and mathematics instruction of teachers who were initially prepared by the Collaboratives for Excellence in Teacher Preparation program (CETP). The focus of this study was on examining the extent to which science and mathematics teachers used more reform‐oriented instructional practices in their classes when they entered the teaching profession. Data were gathered from twelve different CETP projects across the United States. A quasi‐experimental design was used where science and mathematics teachers who were initially prepared by the CETP program were followed into the field and compared to teachers who were not prepared by the CETP program. The results indicate that the teachers prepared by the CETP program used slightly more reform‐oriented instructional practices than teachers who were not prepared by the CETP program, although both mathematics and science teachers reported low levels of reform‐oriented instruction. Implications of results for large‐scale reform of science and mathematics teacher preparation are discussed.