The Quantity and Quality of Biology Laboratory Work in British Columbia High Schools

The purpose of this research was to survey the quantity and quality of laboratory work conducted by 11th- and 12th-grade biology students in British Columbia high schools to analyze student performance on laboratory-based questions on provincial examinations, and to examine the curriculum for recommended laboratory work. A pilot survey was used to produce a valid survey instrument that identified teachers' use of laboratory activities. Examination and curriculum data were extracted from Ministry of Education documents. The frequency of laboratory work was low, with quantitative activities much less frequent than qualitative. Laboratory exercises were confirmatory rather than investigative. Critical thinking and hypotheses formulation were seldom expected of the students. Many teachers reported that they infrequently or never used laboratory simulations or computer-based data collection. Although laboratories were equipped adequately, teachers claimed that the curriculum and provincial examination limited the scope for an inquiry-based course. Provincial examination results indicated that the frequency and type of laboratory work had no effect on scores on lab-based questions. Analysis of the laboratory activities recommended in the syllabus revealed that fewer laboratory activities were being conducted than are recommended in the curriculum guide outline. This study indicates that while the current philosophy of many biology teachers supports an investigative learning experience, little change in classroom practice has occurred in British Columbia schools.     

Condensation of zinc vapor in a supersonic carrier gas

A study of the condensation of a metal vapor in an inert carrier gas is made. Superheated zinc vapor is generated in a hot shot wind tunnel in a helium carrier gas and expanded in a converging-diverging nozzle. Static pressure measurements along the length of the nozzle are made to determine the location of the onset of condensation. A conical nominal Mach 5 (helium) nozzle is employed. The amount of supercooling before the onset of condensation is found to be approximately 430 K, measured along the isentrope over a range of initial zinc mass fractions of .35 to .70 for saturation partial pressures of zinc between 10 psia and 70 psia. The measurements are compared with results of an analysis based on the classical liquid drop model of nucleation. The computed results agree reasonably well with the measurements.     

Increasing the pump-up rate to polarize He gas using spin-exchange optical pumping method

In recent years, polarized ³He gas has increasingly been used as neutron polarizers and polarization analyzers. Two of the leading methods to polarize the ³He gas are the spin-exchange optical pumping (SEOP) method and the meta-stable exchange optical pumping (MEOP) method. At present, the SEOP setup is comparatively compact due to the fact that it does not require the sophisticated compressor system used in the MEOP method. The temperature and the laser power available determine the speed, at which the SEOP method polarizes the ³He gas. For the quantity of gas typically used in neutron scattering work, this speed is independent of the quantity of the gas required, whereas the polarizing time using the MEOP method is proportional to the quantity of gas required. Currently, using the SEOP method to polarize several bar-liters of ³He to 70% polarization would require 20−40 h. This is an order of magnitude longer than the MEOP method for the same quantity of gas and polarization. It would therefore be advantageous to speed up the SEOP process. In this article, we analyze the requirements for temperature, laser power, and the type of alkali used in order to shorten the time required to polarize ³He gas using the SEOP method.     

A principal component analysis based method to discover chemical differences in comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS) separations of metabolites in plant samples

Comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC × GC-TOFMS) provides high resolution separations of complex samples with a mass spectrum at every point in the separation space. The large volumes of multidimensional data obtained by GC × GC-TOFMS analysis are analyzed using a principal component analysis (PCA) method described herein to quickly and objectively discover differences between complex samples. In this work, we submitted 54 chromatograms to PCA to automatically compare the metabolite profiles of three different species of plants, namely basil (Ocimum basilicum), peppermint (Mentha piperita), and sweet herb stevia (Stevia rebaudiana), where there were 18 chromatograms for each type of plant. The 54 scores of the m/z 73 data set clustered in three groups according to the three types of plants. Principal component 1 (PC 1) separated the stevia cluster from the basil and peppermint clusters, capturing 61.84% of the total variance. Principal component 2 (PC 2) separated the basil cluster from the peppermint cluster, capturing 16.78% of the total variance. The PCA method revealed that relative abundances of amino acids, carboxylic acids, and carbohydrates were responsible for differentiating the three plants. A brief list of the 16 most significant metabolites is reported. After PCA, the 54 scores of the m/z 217 data set clustered in three groups according to the three types of plants, as well, yielding highly loaded variables corresponding with chemical differences between plants that were complementary to the m/z 73 information. The PCA data mining method is applicable to all of the monitored selective mass channels, utilizing all of the collected data, to discover unknown differences in complex sample profiles.     

Mechanism and stereoselectivity of a dual amino-catalyzed robinson annulation: rare duumvirate stereocontrol

Computational study of the mechanisms and stereoselectivities of a dual amino-catalyzed synthesis of cyclohexenones containing all-carbon γ-quaternary and ?-tertiary stereocenters is reported. Extensive conformational search with density functional theory optimizations, the high-accuracy SCS-MP2/cc-pV∞Z energies, and PCM solvation corrections were used to characterize all intermediates and transition states. Six mechanisms were considered, all consistent with available experiments. The reaction proceeds via sequential Michael and Mannich conjugate additions whereby the primary amine activates the aldehyde and the catalyst activates the pentenone. We have discovered a rare duumvirate stereocontrol: the Michael reaction sets the enantioselectivity, but both the Michael and the Mannich reactions control the diastereoselectivity.     

Spectra of Random Hermitian Matrices with a Small-Rank External Source: The Critical and Near-Critical Regimes

Random Hermitian matrices are used to model complex systems without time-reversal invariance. Adding an external source to the model can have the effect of shifting some of the matrix eigenvalues, which corresponds to shifting some of the energy levels of the physical system. We consider the case when the n×n external source matrix has two distinct real eigenvalues: a with multiplicity r and zero with multiplicity n−r. For a Gaussian potential, it was shown by Péché (Probab. Theory Relat. Fields 134:127–173, 2006) that when r is fixed or grows sufficiently slowly with n (a small-rank source), r eigenvalues are expected to exit the main bulk for |a| large enough. Furthermore, at the critical value of a when the outliers are at the edge of a band, the eigenvalues at the edge are described by the r-Airy kernel. We establish the universality of the r-Airy kernel for a general class of analytic potentials for r=O(n^g)r=\mathcal{O}(n^{\gamma}) for 0≤γ<1/12.     

Bounded variation in the mean

It is shown that the concept of bounded variation in the mean is not a meaningful generalization of ordinary bounded variation. In fact, it is a characterization of functions which differ from functions of bounded variation on a zero set.

     

Chapter 1:general introduction

One of the most active and continuing subjects in matrix theory during the past century is the study of those linear operators on matrices that leave certain properties or relations of subsets invariant. Such questions are usually called "Linear Preserver Problems." The earliest papers in our reference list are [Frobenius, 1897] and [Kantor, 1897]. Since much effort has been devoted to this type of problem, there have been several excellent survey papers, e.g., [Marcus, 1962], [Marcus, 1971], and [Grone, 1976]. Since the time of Grone's thesis, there have been many developments, encouraged by the introduction of new techniques, many from outside matrix theory itself. We hope this monograph will provide a useful update and convenient reference for the reader. In this introduction, we describe some typical questions and results on linear preserver problems, give some motivation for the study of the subject and finally provide some guidance fur the use of the monograph.     

Validity of linear acoustics for prediction of waveforms caused by sonically moving laser beams

The question is raised as to whether the analysis of the generation of sound by a laser beam moving over a water surface at the sound speed c for an interminable time period requires consideration of nonlinear effects. A principal consideration in this regard is whether the linear acoustics theory predicts a pressure waveform that is bounded in the asymptotic limit when the laser irradiation time is arbitrarily large. It is shown that a bounded asymptotic limit exists when the upper boundary condition corresponds (as is more nearly appropriate) to that of a pressure release surface, but not when it corresponds to that of a rigid surface. The asymptotic solution to the appropriate inhomogeneous wave equation is given exactly for the former case, and it is shown that the highest asymptotic amplitudes, given specified laser power and beam radius a, occur in the limit of a very small light absorption coefficient mu. In this limit, the peak amplitude is independent of mu and occurs at a depth of 0.88/mu. An approximate solution for the pressure waveform at intermediate times establishes that the characteristic time for buildup to the asymptotic limit is of the order of 2.5/(c mu 2a). If this time is substantially shorter than the time that a plane-wave pulse with the asymptotic waveform would take to develop a shock wave, then accumulative nonlinear effects are of minor importance.