12,737 research outputs found

    Intrinsic dissipation in high-frequency micromechanical resonators

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    We report measurements of intrinsic dissipation in micron-sized suspended resonators machined from single crystals of galium arsenide and silicon. In these experiments on high-frequency micromechanical resonators, designed to understand intrinsic mechanisms of dissipation, we explore dependence of dissipation on temperature, magnetic field, frequency, and size. In contrast to most of the previous measurements of acoustic attenuation in crystalline and amorphous structures in this frequency range, ours is a resonant measurement; dissipation is measured at the natural frequencies of structural resonance, or modes of the structure associated with flexural and torsional motion. In all our samples we find a weakly temperature dependent dissipation at low temperatures. We compare and contrast our data to various probable mechanisms, including thermoelasticity, clamping, anharmonic mode-coupling, surface anisotropy and defect motion, both in bulk and on surface. The observed parametric dependencies indicate that the internal defect motion is the dominant mechanism of intrinsic dissipation in our samples

    Spectropolarimetric observations of Herbig Ae/Be Stars I: HiVIS spectropolarimetric calibration and reduction techniques

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    Using the HiVIS spectropolarimeter built for the Haleakala 3.7m AEOS telescope in Hawaii, we are collecting a large number of high precision spectropolarimetrc observations of stars. In order to precisely measure very small polarization changes, we have performed a number of polarization calibration techniques on the AEOS telescope and HiVIS spectrograph. We have extended our dedicated IDL reduction package and have performed some hardware upgrades to the instrument. We have also used the ESPaDOnS spectropolarimeter on CFHT to verify the HiVIS results with back-to-back observations of MWC 361 and HD163296. Comparision of this and other HiVIS data with stellar observations from the ISIS and WW spectropolarimeters in the literature further shows the usefulness of this instrument.Comment: 35 pages, 44 figures, Accepted by PAS

    Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-delay Polarization Modulators

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    Variable-delay Polarization Modulators (VPMs) are currently being implemented in experiments designed to measure the polarization of the cosmic microwave background on large angular scales because of their capability for providing rapid, front-end polarization modulation and control over systematic errors. Despite the advantages provided by the VPM, it is important to identify and mitigate any time-varying effects that leak into the synchronously modulated component of the signal. In this paper, the effect of emission from a 300300 K VPM on the system performance is considered and addressed. Though instrument design can greatly reduce the influence of modulated VPM emission, some residual modulated signal is expected. VPM emission is treated in the presence of rotational misalignments and temperature variation. Simulations of time-ordered data are used to evaluate the effect of these residual errors on the power spectrum. The analysis and modeling in this paper guides experimentalists on the critical aspects of observations using VPMs as front-end modulators. By implementing the characterizations and controls as described, front-end VPM modulation can be very powerful for mitigating 1/f1/f noise in large angular scale polarimetric surveys. None of the systematic errors studied fundamentally limit the detection and characterization of B-modes on large scales for a tensor-to-scalar ratio of r=0.01r=0.01. Indeed, r<0.01r<0.01 is achievable with commensurately improved characterizations and controls.Comment: 13 pages, 13 figures, 1 table, matches published versio

    A simple method for detection of mitochondrial DNA polymorphisms

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    Polymorphisms were identified in mtDNA of Heterobasidion annosum by digesting total genomic DNA with HaeIII, CfoI, or MspI, which recognize the restriction sites GGCC, GCGC, and CCGG, respectively. Most DNA was digested to fragments of less than 2 kb, while AT-rich fragments of 1.7 to 17 kb stood out as bands of uniform intensity after ethidium bromide staining. These fragments hybridized to mtDNA probes and were inherited in a uniparental fashion

    Supporting Primary and Secondary Beginning Teachers Online: Key findings of the Education Alumni Support Project

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    During 2005, the Education Alumni Support Project (EdASP) (Maxwell, Smith, Baxter, Boyd, Harrington, Jenkins, Sargeant & Tamatea 2006) provided online support for University of New England (UNE) graduand, and later, graduate, teachers as they commenced their careers. The project was based on research which reported that many beginning teachers did not get the support they needed as permanent or contract workers, or, as casual, relief or support teachers, and that small scale trials had shown that online support could be effective. One third of beginning teachers who were alumni of UNE in 2004, reported they did not receive adequate or any mentoring. UNE web-based technologies provided the teachers and mentors with online environments for professional and social interaction, and resource sharing. We found that support was especially sought by the project participants in their first school term, and there were differences in the levels of online support sought by secondary and primary beginning teachers. The project raises implications for on-going systemic support for beginning teachers, the issue of transition from students to teachers, as well as questions about teacher education students’ preparation. This paper provides the key findings of the project. Detailed description of the project structure, data collection and data analysis are available in Maxwell et al. (2006)

    The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope

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    We designed, built, and calibrated a new spectropolarimeter for the HiVIS spectrograph (R 12000-49000) on the AEOS telescope. We also did a polarization calibration of the telescope and instrument. We will introduce the design and use of the spectropolarimeter as well as a new data reduction package we have developed, then discuss the polarization calibration of the spectropolarimeter and the AEOS telescope. We used observations of unpolarized standard stars at many pointings to measure the telescope induced polarization and compare it with a Zemax model. The telescope induces polarization of 1-6% with a strong variation with wavelength and pointing, consistent with the altitude and azimuth variation expected. We then used scattered sunlight as a linearly polarized source to measure the telescopes spectropolarimetric response to linearly polarized light. We then made an all-sky map of the telescope's polarization response to calibrate future spectropolarimetry.Comment: PASP 118, June 200

    Opportunities for integrated pest management to control the poultry red mite, Dermanyssus gallinae

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    Dermanyssus gallinae is the most economically important ectoparasite of laying hens in Europe. Control of D. gallinae is already hampered by issues of pesticide resistance and product withdrawal and, with the prohibition of conventional cages in 2012 and the resulting switch to more structurally complex housing which favours red mite, the importance of managing this pest will increase. Integrated Pest Management (IPM), as often employed in agricultural pest control, may be a way to address these issues where a combination of different novel control methods could be used with/without conventional management techniques to provide a synergistic and more efficacious effect. Work at in our laboratory has shown that essential oils including thyme and garlic may act as effective D. gallinae repellents and acaricides, whilst preliminary vaccine studies have demonstrated a significant increase in mite mortality in vitro using concealed antigens. Work elsewhere 27 has considered predators and fungi for D. gallinae control and other husbandry techniques such as manipulating temperature and lighting regimes in poultry units. This paper will review the available and emerging techniques for D. gallinae control and discuss which techniques might be suitable for inclusion in an integrated management programme (e.g. synthetic acaricides and diatomaceous earths)
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