Four-window technique for measuring optical-phase-space-time-frequency tomography

A new approach, the four-window technique, was developed to measure optical phase-space-time-frequency tomography (OPSTFT). The four-window technique is based on balanced heterodyne detection with two local oscillator (LO) fields. This technique can provide independent control of position, momentum, time and frequency resolution. The OPSTFT is a Wigner distribution function of two independent Fourier transform pairs, phase-space and time-frequency. The OPSTFT can be applied for early disease detection

An examination of student perceptions of knowledge transfer in the first-year composition experience

Guided by four research questions, this mixed methods study examined students’ perceptions of their ability to transfer skills learned in the first-year composition (FYC) course to the writing required in their reported majors, in other college courses, and in their vocations. In the quantitative portion of the study, the researcher administered pre- and post-semester composition surveys to capture differences in attitudes in four areas: students’ abilities as writers, students’ previous knowledge of writing, students’ expectations of the FYC course, and students’ expectations of using the knowledge in other courses and contexts. To determine whether there were significant differences in the findings, the researcher used paired-samples t-tests, descriptive statistics, and analysis of variance (ANOVA) tests. The results of the tests for Research Question 1 and for two items mapped to Research Question 3 revealed significant differences. These differences, along with areas where no differences were found, provided insight into students’ perceptions of transfer. In the qualitative portion of the study, analysis of students’ responses to open-ended questions about their perceptions of transfer revealed emergent themes relevant to composition studies: a growing awareness of the conventions of academic discourse; preparation for collegiate and vocational writing; and self-improvement in specific areas of proofreading and editing. The responses of the students emphasized how they had used and how they intended to use the knowledge and skills learned in FYC in their other coursework. Several important recommendations for pedagogy emerged. Perhaps the most important recommendation is to equip instructors with teaching strategies that provide students with the ability to transform knowledge to useable skills. The researcher recommends the research be expanded to a longitudinal study following select students throughout their collegiate writing experiences

Large Quantum Superpositions and Interference of Massive Nanometer-Sized Objects

We propose a method to prepare and verify spatial quantum superpositions of a nanometer-sized object separated by distances of the order of its size. This method provides unprecedented bounds for objective collapse models of the wave function by merging techniques and insights from cavity quantum optomechanics and matter wave interferometry. An analysis and simulation of the experiment is performed taking into account standard sources of decoherence. We provide an operational parameter regime using present day and planned technology.Comment: 4 pages, 2 figures, to appear in PR

Wood-ash recycling affects forest soil and tree fine-root chemistry and reverses soil acidification

Wood ash was applied to a forest ecosystem with the aim to recycle nutrients taken from the forest and to mitigate the negative effects of intensive harvesting. After two years, the application of 8,000 kg ha−1 of wood ash increased soil exchangeable Ca and Mg. Similarly, an increase in Ca and Mg in the Norway spruce fine roots was recorded, leading to significant linear correlations between soil and root Ca and soil and root Mg. In contrast to these macronutrients, the micronutrients Fe and Zn and the toxic element Al decreased in the soil exchangeable fraction with the addition of wood ash, but not in the fine roots. Only Mn decreased in soil and in fine roots leading to a significant linear correlation between soil and root Mn. In soil, as well as in fine roots, strong positive correlations were found between the elements Ca and Mg and between Fe and Al. This indicates that the uptake of Mg resembles that of Ca and that of Al that of Fe. With the wood ash application, the pH increased from 3.2 to 4.8, the base saturation from 30% to 86%, the molar basic cations/Al ratio (BC/Al) of the soil solution from 1.5 to 5.5, and the molar Ca/Al ratio of the fine roots from 1.3 to 3.7. Overall, all below-ground indicators of soil acidification responded positively to the wood ash application within two years. Nitrate concentrations increased only slightly in the soil solution at a soil depth of 75-80 cm, and no signs of increased heavy metal concentrations in the soils or in the fine roots were apparent. This suggests that the recycling of wood ash could be an integral part of sustainable forest management because it closes the nutrient cycle and reverses soil acidificatio

A high-reflectivity high-Q micromechanical Bragg-mirror

We report on the fabrication and characterization of a micromechanical oscillator consisting only of a free-standing dielectric Bragg mirror with high optical reflectivity and high mechanical quality. The fabrication technique is a hybrid approach involving laser ablation and dry etching. The mirror has a reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high-Q high-finesse cavities on chip.Comment: 3 pages, 2 figure

Helicobacter pylori interstrain restriction-modification diversity prevents genome subversion by chromosomal DNA from competing strains

Helicobacter pylori, bacteria that colonize the human gastric mucosa, possess a large number of genes for restriction‐modification (R‐M) systems, and essentially, every strain possesses a unique complement of functional and partial R‐M systems. Nearly half of the H.pylori strains studied possess an active type IIs R‐M system, HpyII, with the recognition sequence GAAGA. Recombination between direct repeats that flank the R‐M cassette allows for its deletion whereas strains lacking hpyIIRM can acquire this cassette through natural transformation. We asked whether strains lacking HpyII R‐M activity can acquire an active hpyIIRM cassette [containing a 1.4 kb kanamycin resistance (aphA) marker], whether such acquisition is DNase sensitive or resistant and whether restriction barriers limit acquisition of chromosomal DNA. Our results indicate that natural transformation and conjugation‐like mechanisms may contribute to the transfer of large (4.8 kb) insertions of chromosomal DNA between H.pylori strains, that inactive or partial R‐M systems can be reactivated upon recombination with a functional allele, consistent with their being contingency genes, and that H.pylori R‐M diversity limits acquisition of chromosomal DNA fragments of ≥1 kb