3,689 research outputs found
Reduced dimension modeling of leading edge turbulent interaction noise
A computational aeroacoustics approach is used to model the effects of real airfoil geometry on leading edge turbulent interaction noise for symmetric airfoils at zero angle of attack. For the first time, one-component (transverse), two-component (transverse and streamwise), and three-component (transverse, streamwise, and spanwise) synthesized turbulent disturbances are modeled instead of single frequency transverse gusts, which previous computational studies of leading edge noise have been confined to. The effects of the inclusion of streamwise and spanwise disturbances on the noise are assessed, and it is shown that accurate noise predictions for symmetric airfoils can be made by modeling only the transverse disturbances, which reduces the computational expense of simulations. Additionally, the two-component turbulent synthesis method is used to model the effects of airfoil thickness on the noise for thicknesses ranging from 2% to 12%. By using sufficient airfoil thicknesses to show trends, it is found that airfoil thickness will reduce the noise at high frequency, and that the sound power P will reduce linearly with increasing airfoil thickness
Roles of Fiscal Policy in New Zealand
Economic growth is one of the objectives of the current government. Fiscal policy, encompassing government expenditure and taxation decisions, can significantly impact on economic growth. This paper proposes a framework which views fiscal policy through three lenses and applies this approach to consider how fiscal policy affects economic growth. The three lenses are: fiscal sustainability, fiscal structure and fiscal stabilisation. The paper reviews international literature pertaining to these three lenses and discusses the extent to which these lenses are incorporated into New Zealandâs current fiscal framework. Contemporary New Zealand fiscal challenges are discussed and, in light of these challenges, the paper concludes with consideration of areas to investigate which may yield improvements to the New Zealand fiscal framework.Fiscal policy, sustainability, stability, structure, taxation, government spending, economic growth
ADA: A NEW PROGRAMMING LANGUAGE.
In an attempt to control defense software costs while maintaining system reliability, the DOD (Department of Defense) has sponsored the development of a new programming language, called Ada. While Ada supports many of the features found in Fortran and Pascal, it has additional features making it easier and more reliable to use in large complex engineering software systems. Currently, the DOD is requiring that many new defense software systems be written in Ada. The author reviews the history of Ada\u27s development and examines the primary constructs of the language. The philosophy behind Ada program design is reviewed by designing and coding a simple program to add two matrices. Ada\u27s future prospects are examined as related to both defense and nondefense applications
FTIR difference and resonance raman spectroscopy of rhodopsins with applications to optogenetics
Thesis (Ph. D.)--Boston UniversityThe major aim of this thesis is to investigate the molecular basis for the function
of several types of rhodopsins with special emphasis on their application to the new
field of optogenetics. Rhodopsins are transmembrane biophotonic proteins with 7
a-helices and a retinal chromophore. Studies included Archaerhodopsin 3 (AR3), a
light driven proton pump similar to the extensively studied bacteriorhodopsin (BR);
channelrhodopsins 1 and 2, light-activated ion channels; sensory rhodopsin II (SRII),
a light-sensing protein that modulates phototaxis used in archaebacteria; and squid
rhodopsins (sRho), the major photopigment in squid vision and a model for human
melanopsin, which controls circadian rythms.
The primary techniques used in these studies were FTIR difference spectroscopy
and resonance Raman spectroscopy. These techniques, in combination with site directed
mutagenesis and other biochemical methodologies produced new knowledge
regarding the structural changes of the retinal chromophore, the location and function
of internal water molecules as well as specific amino acids and peptide backbone.
Specialized techniques were developed that allowed rhodopsins to be studied in intact
membrane environments and in some cases in vivo measurements were made on
rhodopsin heterologously expressed in E. coli thus allowing the effects of interacting
proteins and membrane potential to be investigated.
Evidence was found that the local environment of one or more internal water
molecules in SRII is altered by interaction with its cognate transducer, Htrii, and is
also affected by the local lipid environment. In the case of AR3, many of the broad
IR continuum absorption changes below 3000 cm-1, assigned to networks of water
molecules involved in proton transport through cytoplasmic and extracellular portions
in BR, were found to be very similar to BR. Bands assigned to water molecules
near the Schiff base postulated to be involved in proton transport were, however,
shifted or absent. Structural changes of internal water molecules and possible bands
associated with the interaction with ,8-arrestins were also detected in photoactivated
squid rhodopsin when transformed to the acid Meta intermediate. Near-IR confocal
resonance Raman measurements were performed both on AR3 reconstituted into E.
coli polar lipids and in vivo in E. coli expressing AR3 in the absence and presence of
a negative transmembrane potential. On the basis of these measurements, a model
is proposed which provides a possible explanation for the observed fluorescence dependence of AR3 and other microbial rhodopsins on transmembrane potential
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Expressive vocabulary predicts non-verbal executive function: a 2-year longitudinal study of deaf and hearing children
Numerous studies suggest an association between language and executive function (EF), but evidence of a developmental relationship remains inconclusive. Data were collected from 75 deaf/hard-of-hearing (DHH) children and 82 hearing age-matched controls. Children were 6-11 years old at first time of testing, and completed a battery of nonverbal EF tasks and a test of expressive vocabulary. These tasks were completed again two years later. Both groups improved their scores on all tasks over this period. DHH children performed significantly less well than hearing peers on some EF tasks and the vocabulary test at both time points. Cross-lagged panel models showed that vocabulary at Time 1 predicted change in EF scores for both DHH and hearing children but not the reverse
Chemical ionization tandem mass spectrometer for the in situ measurement of methyl hydrogen peroxide
A new approach for measuring gas-phase methyl hydrogen peroxide [(MHP) CH_3OOH] utilizing chemical ionization mass spectrometry is presented. Tandem mass spectrometry is used to avoid mass interferences that hindered previous attempts to measure atmospheric CH_3OOH with CF_3Oâ clustering chemistry. CH_3OOH has been successfully measured in situ using this technique during both airborne and ground-based campaigns. The accuracy and precision for the MHP measurement are a function of water vapor mixing ratio. Typical precision at 500 pptv MHP and 100 ppmv H_2O is ±80 pptv (2 sigma) for a 1 s integration period. The accuracy at 100 ppmv H_2O is estimated to be better than ±40%. Chemical ionization tandem mass spectrometry shows considerable promise for the determination of in situ atmospheric trace gas mixing ratios where isobaric compounds or mass interferences impede accurate measurements
Resilience in Quaking Aspen: Recent Advances and Future Needs
Quaking Aspen (Populus tremuloides) sustainability is a topic of intense interest in forest ecology. Reports range from declines to persisting or increasing coverage in some areas. Moreover, there is little agreement on ultimate factors driving changes. Low aspen recruitment has been attributed to climate patterns, past management, herbivore increases, competitive interactions with conifers, predator and beaver extirpation, and livestock grazing. Several of these potential causes result from direct or indirect actions of human agency. On June 27â28, 2012 a group of leading aspen ecologists from diverse backgrounds convened at the High Lonesome Ranch in western Colorado to address the state of aspen science under the title, Resilience in Quaking Aspen: restoring ecosystem processes through applied science. The purposes of this meeting were to: (a) present disciplinary updates on recent developments; (b) focus our collective understanding on determining key research gaps; and, to the extent possible, (c) develop a plan to communicate both advances and science gaps to wider audiences. Presentations and group discussions were framed mainly in the geographic context of the western US. The symposium addressed dual central themesâhistorical aspen cover change and ungulate herbivoryâboth of which have important ramifications for future aspen resilience. We also found emergent themes in disturbance, climate work, and genetic innovation. This paper presents a brief review of the state of aspen science and a synopsis of issues and needs identified at the symposium. Detailed treatments of topics mentioned here are found in accompanying articles of this volume. A key recommendation from researchers here is that there are many ââaspen typesââ and novel, landscape- or aspen type-specific, approaches will be required to appropriately address this regional diversity. We further emphasize needed interdisciplinary work addressing changing climates, altered disturbance patterns, intensive herbivory, and human drivers of ecological change
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