“Beyond an acronym,STEM is…”: Perceptions of STEM

Although STEM is at the forefront of many educational initiatives, little is known about various professionals’ perceptions of STEM. This mixed‐methods study surveyed 164 preservice teachers, inservice teachers, administrators, informal educators, and STEM professionals. Quantitative and qualitative questions on the survey elicited participants’ perceptions of STEM, STEM support, and STEM careers. Quantitative analysis revealed that profession influenced understandings of STEM, importance of STEM, support for STEM, and perceptions of STEM career opportunities. Qualitative analysis provided rich explanations for the differences in perceptions among professions. This study suggests that science teacher educators need to ensure preservice teachers have understandings of STEM and STEM careers, K‐16 educators need to emphasize the current importance of STEM, and administrators and policymakers need to align visions of STEM with curriculum and pacing guides so teachers feel supported in their STEM endeavors.     

Analysis of Alaskan crude oils by glass capillary gas chromatography/mass spectrometry

Glass capillary gas chromatography/mass spectrometry is used to profile Alaskan crude oil for purposes of origin verification. Alaskan oil, sampled at Valdez, Alaska, and transshipped to the U.S. East Coast, is compared with 21 samples of foreign crude oil using GC/MS techniques in which original data is reconstructed at selected parent and fragment ions to generate a series of chromatographic profiles. Comparison of selected profiles and compositional parameters derived from peak ratios allows distinction of Alaskan oil from many foreign crudes and may be applied to the examination of crude mixtures.     

Improved passive acoustic band-limited energy detection for cetaceans

Acoustic detection of cetaceans is challenged by the variability of calls and the presence of variable background noise. One detection method is to start with frequency band-limited signal and noise estimates, and apply a likelihood ratio test (LRT). These detectors suffer from false alarms when broadband signals overlap the band of interest, triggering detection. Some detectors only consider previous samples, causing further false alarms. The authors propose a method of reducing false alarms by defining a guard band that is not expected to contain energy from the species of interest. A second LRT is performed by testing the ratio of the signal estimate in the signal band with the signal estimate of the guard band. This method is shown to reduce false alarms with a small reduction in detection performance. A detection method is also presented that can be optimized for high processing efficiency, while improving false-alarm rejection from signals that are longer in duration than the signal of interest. Performance is demonstrated on real cetacean recordings and ocean noise. The detection algorithm is implemented in PAMGUARD, an open source Java application designed for passive acoustic monitoring (PAM) of cetaceans.     

The assignment of the ionization potentials of formaldehyde by an (e, 2e) experiment

The angular variation of the binding energy spectrum in an electron-electron coincidence experiment indicates that the third and fourth ionization potentials of formaldehyde are due to the 5a₁ and 1b₂ orbitals respectively. The vertical ionization potentials of the 4a₁ and 5a₁ orbitals are found to be 21.15 ± 0.15 and 34.2 ± 0.2 eV respectively.     

Rapid and simultaneous analysis of some bioactive components in Eucommia ulmoides by capillary electrophoresis

A micellar electrokinetic chromatography method was established for the qualitative and quantitative determination of three groups of bioactive components, iridoids, flavonoids and phenolic compounds, in Eucommia ulmoides. Of the eleven bioactive components being studied, ten were successfully separated in 50 mM boric acid buffer at pH 9.5, with 50 mM sodium dodecylsulfate and 4% 1-butanol, at a voltage of 20 kV, temperature of 20 degrees C and injection under high pressure at 138 kPa for 5 s in a fused-silica capillary with peak detection at 214 nm. A high reproducibility and good linearity was obtained. The relative standard deviations of the migration times in eight injections of the standards ranged from 0.64 to 1.88% and those of the corrected peak area ranged from 2.79 to 6.62%. A good linearity, with correlation coefficients in the range of 0.995-1.000, was obtained in the calibration curves of each standard from 1 to 50 ppm. The amount of these bioactive components in the bark and leaves of Eucommia ulmoides were determined.     

Application of capillary electrophoresis- electrospray-mass spectrometry to the separation and characterization of isomeric lipopolysaccharides of Neisseria meningitidis

A capillary electrophoresis-electrospray-mass spectrometry technique for the characterization of lipopolysaccharides (LPSs) was developed, permitting the separation of trace-level O-deacylated LPS isoforms for subsequent structural characterization using tandem mass spectrometry (MS/MS). The separation buffer and electrospray interface were optimized first using O-deacylated LPS samples from large-scale preparations. It was found that with microelectrospray or sheath-solution interface, we could separate LPS in anionic forms and detect them using either negative or positive ion mode MS. For negative ion detection mode MS, 30 mM morpholine with addition of 5% v/v methanol was employed as separation buffer. When positive ion detection mode MS was required, 10 mM ammonium acetate with addition of 5% methanol was used as separation buffer. The structural assignments obtained from MS/MS and capillary zone electrophoresis-electrospray-MS (CZE-ESMS) analyses enabled the identification of isomeric glycoforms. Application of this technique to the analysis of LPS from the galE mutants of Neisseria meningitidis strain BZ157 B5+ revealed the presence of isomeric glycoforms, in which the location of a functional group phosphoethanolamine was found to be in either inner core or lipid A-OH regions. The described technique was also applied to the analysis of LPS samples from the galE mutant of N. meningitidis strains F1576 A4+ and A4-. The occurrence of isomeric LPS glycoforms differing by the location or presence of neutral sugar residues, such as hexoses, can also be characterized using MS/MS.     

The effects of different copper (and some other) catalysts on the conversion of triphenyl- and tetraphenyl- diazocyclopentadienes and of some phenyliodonium αα′-dicarbonylylides into arsonium and other ylides

Diazo-compounds or iodonium ylides may be converted into arsonium and other ylides when heated in solution with triphenylarsine or other suitable carbene (or carbenoid) acceptor, and with a suitable Cu derivative present. The effects of using different copper complexes and salts are described and discussed. Other metal derivatives were for the most part ineffective as catalysts.     

Imaging as a tool for improving length and accuracy of sequence analysis in automated fluorescence-based DNA sequencing

A new method of signal analysis for automated fluorescence-based DNA sequencing is presented. Signal resolution is a limiting factor in obtaining accurate sequence information beyond 400-450 nucleotides per gel lane. We have developed a computer program for the imaging of DNA bands in sequencing gels. The image analysis shows that distortions in the shapes of the bands decrease resolution of peaks observed served in the standard data plots. Reconstruction of the undistorted band shape prior to signal analysis substantially improves the resolution of peaks and may improve the accuracy and length of the contiguous sequence read. Image analysis identified other factors limiting the accuracy and length of automated DNA sequence analysis and provided a tool for evaluating various remedies. Our techniques should also be applicable in other systems, for example, in gel electrophoresis of proteins and DNA restriction fragments, and in scranning densitometry.     

On the latitudinal and radial motion of timelike vortical trajectories in the Kerr metric

The timelike vortical geodesies of the Kerr metric are integrated numerically in ther- subspace of the Boyer-Lindquist coordinates. We find that the trajectories, under physically reasonable conditions, are essentially conical (in the sense of constant). This behavior is not that which one would infer from previous qualitative discussions.