Interferometric technique for measuring broadband ultrashort pulses at the sampling limit

We present a new technique for measuring ultrashort optical pulses by use of spectral phase interferometry for direct electric-field reconstruction that is suitable for large bandwidth pulses. The method does not require generation of a replica of the pulse to be measured and encodes the spectral phase information in a spatial interference pattern. A major advantage of this method is that the spectral sampling saturates the Whittaker-Shannon bound. Moreover, the technique allows for the characterization of some types of space-time coupling. An experimental demonstration of the technique is presented.     

Surface crystallization of amorphous solid water

We demonstrate that the crystallization of thin, supported amorphous solid water layers is initiated at the water surface. This is concluded from the observation of sequential crystallization of amorphous water at the surface, in the bulk, and at the water-support interface. A surface nucleation model quantitatively reproduces the observed transformation kinetics at the three sites.     

A more sensitive MS detector does not obviously lead to a more sensitive assay: experiences with ES-285

In this paper the transfer of an existing method for the quantitative determination of the anticancer agent ES-285 in human plasma using liquid chromatography tandem mass spectrometry on an API 365 to an API 3000 mass spectrometer is described. The transfer appeared not to be straightforward. Problems arose resulting from carry-over and interferences. In addition, due to the expansion of the calibration range, data ought to be weighted with a different factor to increase the accuracy of the lower concentrations. After finding appropriate solutions for these problems, the lower limit of quantitation could be lowered from 10 to 1 ng/mL for ES-285 in human plasma. The usefulness and necessity of the modified assay was demonstrated by analysis of plasma samples from a patient receiving a low dosage of the drug.     

Vocal Tract Resonance Analysis of Aging Voice Using Long-Term Average Spectra

This study is the first to use long-term average spectra (LTAS) to investigate resonance characteristics of dynamic speech in young adulthood and old age. A total of 80 speakers participated, divided equally by age group and gender. All elderly speakers were healthy, active members of the community. Measurement of the first three spectral peaks in LTAS from the first paragraph of the Rainbow Passage revealed significant lowering of peak 1 from young adulthood to old age in both men and women. Peaks 2 and 3 also lowered significantly across the adult lifespan in women and showed a tendency to lower in men. These acoustic findings are consistent with anatomic data suggesting that aging results in lengthening of the supraglottic vocal tract. Findings that women demonstrate more substantial lowering of spectral peaks with aging than men suggest that women may undergo more pronounced age-related lengthening of the supraglottic vocal tract. Alternatively, it is possible that elderly men systematically alter tongue position during vowel articulation while elderly women are less inclined to do so. Taken in conjunction with previous research, these findings suggest a "mixed model" of vocal tract resonance changes with aging in which an interaction exists between gender, the resonance effects of laryngeal lowering, and vowel articulatory patterns.     

How Students “Unpack” the Structure of a Word Problem: Graphic Representations and Problem Solving

This research investigated how fourth and fifth grade students spontaneously ‘unpacked’ a word problem when generating a graphic representation to aid in problem solution. Relationships among the type of graphic representation produced, spatial visualization, drawing ability, gender, and problem solving also were examined and described. Instrumentation developed for the study included several math challenge tasks, a spatial visualization task, and a drawing task. For one of the math challenge tasks, students were instructed to draw a picture to assist them with problem solution. These graphic representations generated by students were rated as pictorial or as displaying some level of schematic representation. Schematic representations included germane information from the problem supportive of problem solution. Pictorial representations included expressive and extraneous elements not necessary for problem solution, with no schematic elements. Findings indicated that the majority of students rendered schematic representations, with girls more likely than boys to use schematic representations at a statistically significant level. Students who used schematic visual representations were more successful problem solvers than those pictorially representing problem elements. The more “schematic‐like” the visual representation, the more successful students were at problem solution. Drawing a pictorial representation in the math challenge task also was negatively correlated to drawing skill.     

Spontaneous Assembly of Magnetic LEGO Bricks

This paper describes simple methods of demonstrating macroscale spontaneous assembly. These demonstrations can illustrate topics in college or high school chemistry courses, such as the thermodynamics of crystallization and the chelate effect. The assembling units are built from a combination of magnetic and conventional LEGO building blocks. Unlike many other spontaneous-assembly experiments, these assemblies do not require surface flotation to form.