Development of a HgCdTe photomixer and impedance matched GaAs FET amplifier

A research program for the development of a 10.6 micron HgCdTe photodiode/GaAs field effect transistor amplifier package for use at cryogenic temperatures (77k). The photodiode/amplifier module achieved a noise equivalent power per unit bandwidth of 5.7 times 10 to the 20th power W/Hz at 2.0 GHz. The heterodyne sensitivity of the HgCdTe photodiode was improved by designing and building a low noise GaAs field effect transistor amplifier operating at 77K. The Johnson noise of the amplifier was reduced at 77K, and thus resulted in an increased photodiode heterodyne sensitivity

Taking the pulse of snowmelt: in situ sensors reveal seasonal, event and diurnal patterns of nitrate and dissolved organic matter variability in an upland forest stream

Highly resolved time series data are useful to accurately identify the timing, rate, and magnitude of solute transport in streams during hydrologically dynamic periods such as snowmelt. We used in situ optical sensors for nitrate (NO3 −) and chromophoric dissolved organic matter fluorescence (FDOM) to measure surface water concentrations at 30 min intervals over the snowmelt period (March 21–May 13, 2009) at a 40.5 hectare forested watershed at Sleepers River, Vermont. We also collected discrete samples for laboratory absorbance and fluorescence as well as δ18O–NO3 − isotopes to help interpret the drivers of variable NO3 − and FDOM concentrations measured in situ. In situ data revealed seasonal, event and diurnal patterns associated with hydrological and biogeochemical processes regulating stream NO3 − and FDOM concentrations. An observed decrease in NO3 − concentrations after peak snowmelt runoff and muted response to spring rainfall was consistent with the flushing of a limited supply of NO3 − (mainly from nitrification) from source areas in surficial soils. Stream FDOM concentrations were coupled with flow throughout the study period, suggesting a strong hydrologic control on DOM concentrations in the stream. However, higher FDOM concentrations per unit streamflow after snowmelt likely reflected a greater hydraulic connectivity of the stream to leachable DOM sources in upland soils. We also observed diurnal NO3 − variability of 1–2 μmol l−1 after snowpack ablation, presumably due to in-stream uptake prior to leafout. A comparison of NO3 − and dissolved organic carbon yields (DOC, measured by FDOM proxy) calculated from weekly discrete samples and in situ data sub-sampled daily resulted in small to moderate differences over the entire study period (−4 to 1% for NO3 − and −3 to −14% for DOC), but resulted in much larger differences for daily yields (−66 to +27% for NO3 − and −88 to +47% for DOC, respectively). Despite challenges inherent in in situ sensor deployments in harsh seasonal conditions, these data provide important insights into processes controlling NO3 − and FDOM in streams, and will be critical for evaluating the effects of climate change on snowmelt delivery to downstream ecosystems

The Basset Horn: Its Development and Literature

The purpose of this study is to trace the development of a practically extinct woodwind instrument, the basset horn, and its use by composers as both a solo and an orchestral instrument. The first chapter concerns the development of the basset horn from the earliest imperfect specimen to the modern-day instrument. The second chapter deals with the physical characteristics that are peculiar to the instrument. The third chapter discusses the literature and musical history of the basset horn. An appendix provides a comprehensive listing of literature for the instrument

Hidden Error Variance Theory. Part II: An Instrument That Reveals Hidden Error Variance Distributions from Ensemble Forecasts and Observations

Abstract In Part I of this study, a model of the distribution of true error variances given an ensemble variance is shown to be defined by six parameters that also determine the optimal weights for the static and flow-dependent parts of hybrid error variance models. Two of the six parameters (the climatological mean of forecast error variance and the climatological minimum of ensemble variance) are straightforward to estimate. The other four parameters are (i) the variance of the climatological distribution of the true conditional error variances, (ii) the climatological minimum of the true conditional error variance, (iii) the relative variance of the distribution of ensemble variances given a true conditional error variance, and (iv) the parameter that defines the mean response of the ensemble variances to changes in the true error variance. These parameters are hidden because they are defined in terms of condition-dependent forecast error variance, which is unobservable if the condition is not sufficiently repeatable. Here, a set of equations that enable these hidden parameters to be accurately estimated from a long time series of (observation minus forecast, ensemble variance) data pairs is presented. The accuracy of the equations is demonstrated in tests using data from long data assimilation cycles with differing model error variance parameters as well as synthetically generated data. This newfound ability to estimate these hidden parameters provides new tools for assessing the quality of ensemble forecasts, tuning hybrid error variance models, and postprocessing ensemble forecasts

Jazz and gender : teaching improvisation to girls

The purpose of this study is to examine the reasons that girls do not pursue advanced jazz education and to suggest teaching strategies that could encourage greater female participation. I have observed that the number of female students is approximately equal to that of the male students in concert band, and in a concert band setting these girls do seem to advance more quickly than boys. Through literature review and interviews with music educators and female jazz musicians, this study will examine whether some of the teaching techniques that allow girls to succeed in concert band could be adapted to facilitate success in the jazz band setting. In particular, the following questions will be addressed: 1. Do girls learn jazz improvisation differently than boys? 2. If so, should music educators utilize teaching strategies to accommodate these differences

Synthesis of luminescent europium defects in diamond

© 2014 Macmillan Publishers Limited. All rights reserved. Lanthanides are vital components in lighting, imaging technologies and future quantum memory applications owing to their narrow optical transitions and long spin coherence times. Recently, diamond has become a pre-eminent platform for the realisation of many experiments in quantum information science. Here we demonstrate a promising approach to incorporate Eu ions into diamond, providing a means to harness the exceptional characteristics of both lanthanides and diamond in a single material. Polyelectrolytes are used to electrostatically assemble Eu(III) chelate molecules on diamond and subsequently chemical vapour deposition is employed for the diamond growth. Fluorescence measurements show that the Eu atoms retain the characteristic optical signature of Eu(III) upon incorporation into the diamond lattice. Computational modelling supports the experimental findings, corroborating that Eu(III) in diamond is a stable configuration. The formed defects demonstrate the outstanding chemical control over the incorporation of impurities into diamond enabled by the electrostatic assembly together with chemical vapour deposition growth

Rat mammary carcinogenesis following neutron- or X-radiation

Female 61 to 63 - day - old Sprague-Dawley rats were exposed once to a single dose of either 0.43 - MeV neutrons or 250 - kVX - rays . For neutrons 23 rats were exposed in plastic tubes rotated around and 31 c m from a water-cooled tritium impregnated target bombarded with 2.45 - MeV protons from a V a n de Graaff generator. The mean kerma was measured at the rat location by integrating the response of a rat - sized homogeneous tissue equivalent ionization chamber of minimum mass. The ratio between absorbed dose and kerma is under investigation and is anticipated to be approximately 0.7. A compensated GM gamma-ray dosimeter indicated that the gamma - ray doses were 3.5% of the total dose. All rats were examined weekly for the presence of breast tumours and these were removed, fixed, stained and verified histologically as mammary neoplasms. At 10 months after exposure 98<7ο of the rats were a live . The neutron kerma, the per cent of rats with mammary neoplasia, and the number of rats were, respectively: 0.125 rads, 8.2°}o, 182; 0.5 rads, 9.0^0, 89; 2 rads, 20. 6,68; and 8 rads, 31.1%, 45. The X - ray results were: 30 R, 1.4% 95; 60 R, 27. l°Io, 48; and 90 R, 35.4%, 48. A 3. O^o incidence was found in 167 control rats. At 10 months after exposure the mammary neoplastic response after 8 rads of neutrons corresponds approximately to that after 60 - 90 R of X - rays . Similarly, the response after 2 rads of neutrons was intermediate between 30 and 60 R of X - rays and the response after 0 . 125 and 0.5 rads of neutrons was similar to that after 30 R of X - rays . This demonstrates that the RBE for 0.43 - MeV neutrons is much lower at high doses than at low doses. Determination of the confidence limits for the dose-RBE dependence and dose-incidence relationship will be determined as additional data are collected

Systems modelling predicts chronic inflammation and genomic instability prevent effective mitochondrial regulation during biological ageing

The regulation of mitochondrial turnover under conditions of stress occurs partly through the AMPK-NAD+-PGC1α-SIRT1 signalling pathway. This pathway can be affected by both genomic instability and chronic inflammation since these will result in an increased rate of NAD+ degradation through PARP1 and CD38 respectively. In this work we develop a computational model of this signalling pathway, calibrating and validating it against experimental data. The computational model is used to study mitochondrial turnover under conditions of stress and how it is affected by genomic instability, chronic inflammation and biological ageing in general. We report that the AMPK-NAD+-PGC1α-SIRT1 signalling pathway becomes less responsive with age and that this can prime for the accumulation of dysfunctional mitochondria